LOS ANGELES >> When federal immigration agents visited Los Angeles 7-Eleven stores and trucking companies near the ports in recent weeks to conduct audits of employee records, it sent a chill through those businesses and others in the region.

Immigrant advocates said some employees at the audited firms stopped coming to work. Workers at other companies worried they could be next. And their employers were concerned — or confused — enough that trade groups and attorneys distributed tip sheets advising companies of what federal and state law requires them to do as the Trump administration and California wage war over immigration policy.

“There is a heightened level of stress and anxiety,” said Alexandra Suh, executive director of the Koreatown Immigrant Workers Alliance, which helps low-wage immigrant workers in the Los Angeles neighborhood. “Even just the request for documentation caused a number of workers to quit on the spot.”

Here’s a look at what’s behind the federal activity, and how it will impact businesses.

WHAT IS ICE LOOKING FOR?

Immigration and Customs Enforcement, under the Trump administration, has promised to beef up work site enforcement, as well as increase its presence in so-called sanctuary jurisdictions such as California.

In the recent five-day operation, ICE agents served 122 notices to L.A.-area companies that they would be conducting an audit of their I-9 forms. Several weeks earlier, the same notices were given to 77 companies in Northern California.

I-9s are the forms on which employees attest to their work status and present documents to support that they are who they say they are and have the authorization to work.

After getting that notice, employers must produce documents in as little as three business days.

If ICE determines that the documents show an employee is unauthorized to work, the employer is notified they could face civil and criminal penalties if they continue to employ that person.

Employers can then speak privately with specific employees to try to correct any document discrepancies. More often than not, even though immigration authorities don’t attend such meetings, employees simply disappear rather than show up, according to advisory documents employment attorneys circulated to fruit growers last year.

WHAT FEDERAL LAW REQUIRES

It is illegal for employers to knowingly hire workers in the country illegally, and they must take some steps to verify employees are authorized to be here.

For the I-9 form, an employee presents proof such as a U.S. passport, green card or Social Security number along with a government or school photo ID.

Employers who do not keep the proper paperwork can face fines, with larger financial penalties levied against people who knowingly hire undocumented workers.

Individuals who engage in a “pattern or practice” of hiring unauthorized workers can face criminal charges and more substantial monetary fines.

But some experts say the penalties are too weak, watered down to appease business interests so as to allow companies to look the other way. Bryan Little, director of employment policy for the California Farm Bureau Federation, said most employers don’t seek to hire undocumented workers, but documents are often faked.

If employers do not accept a document that “reasonably appears to be genuine and to relate” to the worker, though, they can face discrimination charges.

“You are not required to be a document examiner,” said Danielle H. Gotcher, managing partner of Global Immigration Partners in Calabasas Hills.

ARE ICE’S AUDITS NEW?

No. ICE visits to employers hit a peak of 3,127 under President Obama in 2013, before his administration shifted its focus to deporting people convicted of serious crimes. In the 2017 fiscal year, ICE said it conducted 1,360 audits.

But under Trump, who railed against both legal and illegal immigration during both the 2016 campaign and his presidency, ICE agents have become more willing to arrest anyone in the country illegally whom they encounter during enforcement actions, even if those people have no criminal convictions.

In the 2017 fiscal year, which included the last few months of the Obama administration and most of Trump’s first year in office, immigration arrests inside the country of people with criminal convictions jumped 12 percent. Arrests of people with no criminal convictions more than doubled, to more than 37,000.

Actual deportations were down 6 percent, partly because of a sharp drop in arrests of people trying to cross the border in the first place.

ICE has promised to get more aggressive, and Deputy Director Thomas Homan has said he wants to ramp up work site enforcement by 400 percent.

WHAT’S THE RATIONALE FOR TRUMP’S CRACKDOWN?

Dani Bennett, an ICE spokesperson, said workplace audits are needed to protect jobs for people here legally and “eliminate unfair competitive advantages for companies that hire an illegal workforce.”

Some economists say immigrants, particularly undocumented workers, have depressed wages for Americans in low-paying jobs, because they expand the labor pool and are willing to work for less.

But there is disagreement among experts on the extent of the effect and whether it even exists.

Dave Smith, an economist at the Pepperdine University Graziadio School of Business and Management, said undocumented workers have a slight negative impact on wages of low-skilled workers, but automation and the nation’s shift away from manufacturing have been much bigger factors.

Giovanni Peri, director of the Migration Research Cluster at UC Davis, doesn’t believe immigrants have pushed wages down. Instead, immigrants, regardless of legal status, provide a boost to the economy, he said — more people buying more goods and services.

Studies show immigrants start businesses at a higher rate than native-born Americans. Peri said undocumented workers take manual labor jobs that many here legally don’t want.

“Without them it would be a much smaller economy,” Peri said.

WHAT INDUSTRIES GET HIT HARDEST BY A CRACKDOWN?

An estimated 11 million people are believed to be living in the United States illegally. About 10 percent of California’s workforce is in the country illegally, according to estimates from the Center for the Study of Immigrant Integration at USC.

Some industries, such as agriculture and construction, have a much heavier concentration of undocumented workers.

According to USC researchers, undocumented people account for 45 percent of agricultural employment in California. In construction, it is 21 percent. Undocumented workers account for 17 percent of employees in a broad sector that includes accommodation and food services. Other industries with significant numbers of undocumented workers are manufacturing and wholesale trade.

Both agriculture and construction are facing a shortage of workers, which has those companies concerned about losing immigrant workers. Among the reasons for the shortage, they say, is declining immigration from Mexico.

If the Trump administration ramps up deportations — and succeeds in persuading Congress to limit legal immigration — worker shortages would worsen, Smith said. Construction projects would take longer to complete, and some crops would go unpicked.

“The crackdown on immigration … could have a pull-back effect on the California economy, which I think has benefited greatly from an infusion of labor over time,” he said.

Several years ago, similar I-9 audits in the Central Coast led to layoffs. And growers began recruiting foreign agricultural guest workers through the H-2A visa program.

The California Fresh Fruit Assn. told growers in early February that federal authorities were revisiting packinghouses that had been audited within the last five years — something that in the past has sent workers fleeing.

“Even their presence in an office causes people to leave,” association President George Radanovich said. “We’re very concerned about it and we wish the federal government would get its immigration act in order.”

During a recent two-day tour of the Central Valley, Agriculture Secretary Sonny Perdue assured growers that he had spoken privately with officials at Homeland Security, the agency that houses ICE, and cautioned them that public raids can wreak havoc on the industry.

“People are not going to their jobs, because they’re afraid,” Hortencia Solario, a worker at Harris Woolf California Almonds, told Perdue during a stop-over at the company’s processing facility in Coalinga.

“The good news is President Trump gets what you’re saying,” Perdue replied. “The people who are out here working and paying taxes — in this plant or in other places — are not the people he is after.”

WHAT PROTECTION DOES CALIFORNIA LAW PROVIDE?

A new state law, AB 450, limits how cooperative California businesses can be with federal immigration authorities.

Employers now cannot allow immigration agents into “nonpublic” areas of a business without a judicial warrant, for instance. Nor can they voluntary let agents access employee records without a subpoena, a warrant from a judge or a notice of I-9 inspection. And employers are now required to notify all employees of an I-9 audit within three days of being served an audit notice.

Another new state law also limits cooperation between local law enforcement and ICE agents.

ICE’s Homan has said he is increasing the agency’s presence in California, because the new limitations force it to conduct large-scale sweeps. In a separate Los Angeles operation, conducted at the same time as the I-9 audits, ICE agents arrested 212 people in the country illegally.

Sue M. Bendavid, an employment attorney with Lewitt Hackman in Encino, said some of her business clients are confused over their responsibility under AB 450 and how that could conflict with the demands of federal agents. One client contacted her after ICE agents visited a nearby business, wondering if they were next.

“AB 450 really puts employers in between a rock and hard place,” she said.

In a news release announcing the recent operations in the L.A. area, ICE said California’s new workplace law intends “to interfere with federal immigration enforcement authorities” and it “expects employers and state officials to comply with federal law.” However, Bennett, the ICE spokeswoman, declined to say whether the agency believes any part of AB 450 violates federal law.

California Atty. Gen. Xavier Becerra and Labor Commissioner Julie Su released an advisory and FAQ this month, and they insist there are no conflicts between the state law and federal requirements.

“The Immigrant Worker Protection Act seeks first and foremost to protect Californians’ privacy at the workplace,” Becerra said in a recent statement.

WHAT OTHER RISKS DO AUDITS POSE FOR EMPLOYEES?

While ICE says it focuses on individuals who pose a threat to national security, public safety and border security, it also says it no longer looks the other way if agents come across people without criminal convictions who are here illegally. ICE has expanded the number of people it considers priorities for deportation.

Cinthia Flores, a staff attorney with the Coalition for Humane Immigrant Rights of Los Angeles, said she worries that I-9 audits will be used as leads to find and deport workers fired for suspect documents.

“That is our biggest concern,” she said. Beyond losing a job, “there is not supposed to be any kind of consequences for workers.” ICE confirmed that depending on the circumstances, it’s possible the agency would go after a person after he or she is fired.