WASHINGTON >> As federal investigators in Delaware were examining the finances of Hunter Biden during his father’s campaign for president, a similar inquiry ramped up this year in Pittsburgh, fueled by materials delivered by President Donald Trump’s personal lawyer Rudy Giuliani.

Attorney General William Barr had asked the top federal prosecutor in Pittsburgh, Scott Brady, to accept and vet any information that Giuliani had on the Biden family, including Hunter Biden. Brady hosted Giuliani for a nearly four-hour meeting in late January to discuss his materials.

The arrangement immediately raised alarms within the FBI and the Justice Department. Giuliani had served as Trump’s attack dog during the Russia investigation before becoming the face of an effort to tarnish Hunter Biden during President-elect Joe Biden’s campaign. If Brady’s investigation became public, the agents feared that the FBI could be drawn into a politically toxic battle in the midst of the presidential election, just as it was in 2016.

The officials worried about how the Justice Department, which they saw as trying to placate the president, would handle the inquiry. Some prosecutors and agents in Pittsburgh regarded Brady as a Trump loyalist who was thought to be angling to run for office, and they expressed concern that Brady was wielding the FBI as a weapon to damage Biden’s candidacy. At one point, Brady made clear that he wanted the U.S. attorney in Delaware, David C. Weiss, to continue his investigation, even though Brady is not authorized to direct other federal prosecutors’ offices.

This account is based on interviews with five current and former law enforcement officials and others with knowledge of FBI interactions with the Justice Department. Most spoke on the condition of anonymity to discuss continuing federal investigations.

Giuliani himself was also the focus of a criminal investigation in New York over his dealings in Ukraine, including his effort to oust the U.S. ambassador to the country, which was at the heart of the impeachment trial. And the Pittsburgh investigation appeared to be parallel to the existing inquiry in Delaware.

Brady has not brought any criminal charges, and Barr has not publicly discussed the investigation’s status since revealing in February that the department would accept Giuliani’s material.

Hunter Biden disclosed this week that prosecutors in Delaware were continuing to investigate him for possible federal tax crimes, serving multiple subpoenas Tuesday to Hunter Biden and his business associates after apparently going dormant in the run-up to the election. The investigation appeared focused on his dealings with China and with Burisma Holdings, the Ukrainian gas company on whose board he served, according to people familiar with the matter.

Legal experts said that prosecutors could be examining how Biden obtained the money to pay hundreds of thousands of dollars in tax liens this year.

The president-elect is not under investigation. But the disclosure of a criminal inquiry into his son thrust Joe Biden into a charged position as he prepares to take office. Republican senators called for an independent special counsel to investigate Hunter Biden, and Trump complained that the Delaware inquiry did not surface before the election.

“I’m proud of my son,” Biden told reporters Friday.

The FBI and the Justice Department declined to comment. Giuliani did not respond to a request for comment.

In 2018, the FBI and the U.S. attorney’s office in Wilmington, Delaware, quietly began investigating whether Hunter Biden had violated money laundering laws, according to people with knowledge of the inquiry.

Investigators eventually determined that the money laundering aspect of the Hunter Biden inquiry was not going to lead to charges. But they had discovered potential tax law violations and felt they had the makings of a strong tax case against him, according to several people familiar with the matter. The inquiry came to involve IRS agents.

Separately, Giuliani was collecting information in Ukraine that could benefit Trump by hurting his perceived rivals, including Biden. Giuliani had tried to promote scrutiny of Hunter Biden’s work for Burisma, which had been mired in a corruption scandal. He accused Joe Biden of corruptly pushing for the ouster of Ukraine’s top prosecutor, who had been investigating Burisma, as a favor to his son while he was vice president. No evidence of wrongdoing by the president-elect has emerged.

Trump’s pressure campaign on the Ukrainian government to announce investigations that could help him politically was the focus of his impeachment. Giuliani sought during the impeachment to equate his allegations about Hunter Biden with the accusations that Trump had abused his power.

He also continued to wage his campaign to further any investigations that could benefit Trump by damaging his opponents. Giuliani’s lawyer, Robert Costello, asked the Justice Department for a meeting to discuss what he felt was explosive information about Hunter Biden that he had gathered from people in Ukraine and elsewhere, according to a person with direct knowledge of the matter.

In response, Brady called Costello and offered to meet. Giuliani and Costello sent reams of documents to Pittsburgh, then traveled there on Jan. 29. They were picked up by FBI agents and stopped for breakfast before meeting for nearly four hours at the local FBI office with Brady and his top deputies on the inquiry, Stephen Kaufman and Ira Karoll, the person said.

Costello had several ensuing conversations with Brady’s office, including as recently as this summer, about the Bidens. Costello and Giuliani also recommended a handful of potential witnesses in the United States and Ukraine for the FBI to interview, but Costello said the FBI never followed through.

At a news conference about a week after the meeting, Barr announced that he had created an intake process for information about Ukraine to “assess its provenance and its credibility.”

He did not mention Pittsburgh, nor the meeting. Barr cautioned that investigators had to be careful about any information coming from Ukraine, including from Giuliani. “There are a lot of agendas in the Ukraine, a lot of crosscurrents,” Barr warned. “And we can’t take anything we received from Ukraine at face value.”

The investigation in New York into Giuliani also set up a potentially messy situation that might allow him to leverage the work in Pittsburgh — and his role as a potential witness in any case — against a prosecution in New York.

Federal law enforcement officials also feared that Giuliani was submitting questionable information to the Justice Department to make it seem more credible than it really was. They said that it was impossible to separate his efforts from his crusades on behalf of the president, and some told associates that he could damage the department’s credibility by forcing investigators to examine issues that seemed like nothing more than conspiracy theories.

Officials said that Brady almost immediately started pushing to take aggressive steps. He had a list of people he wanted FBI agents to question. It was not clear whether they were the same witnesses that Giuliani and Costello had submitted, but a former law enforcement official said that Brady had wanted the FBI to question people mentioned in Giuliani’s materials.

The steps were outside “normal investigative procedures,” one former senior law enforcement official with knowledge of the events said, particularly in an election year; Justice Department policy typically forbids investigators from making aggressive moves before elections that could affect the outcome of the vote if they become public.

The Pittsburgh FBI office refused to comply without the approval of David Bowdich, the FBI’s deputy director, the former official said.

Brady’s demands soon prompted a tense confrontation with FBI officials at the bureau’s headquarters in Washington. The meeting was mediated by Seth DuCharme, now the acting U.S. attorney in Brooklyn and at the time a trusted aide and ally of Barr’s at the Justice Department in Washington.

The FBI viewed the investigative steps into Hunter Biden that Brady sought as unwarranted because the Delaware inquiry involving money laundering had fizzled out and because they were skeptical of Giuliani’s material. For example, they had already examined a laptop owned by Biden and an external hard drive that had been abandoned at a computer store in Wilmington and found nothing to advance the inquiry.

Investigators were also worried that the effort might become public — particularly any interviews of witnesses who were Giuliani’s sources of information — and could drag the FBI back into presidential campaign politics, the same turbulent path it had stumbled down in 2016 with investigations into Hillary Clinton’s private email server and the Trump campaign’s ties to Russia.

Still, Brady pressed the FBI to do more, officials said. The agents found ways to ostensibly satisfy Brady without upending the election. It is not clear how they compromised, but agents could have investigated more discreetly, like questioning witnesses they were confident would keep quiet or checking databases.