SAN ANTONIO >> Investigators believe a truck driver accused in the deaths of 10 people found inside a packed, sweltering tractor-trailer is just one member of a larger organization involved in human smuggling that they are looking to identify and dismantle, a U.S. immigration official said today.

Some of the 29 identified survivors have told authorities they hired smugglers who brought them across the U.S. border, loaded some of them onto trucks that took them to the tractor-trailer, and marked them with different colored tape to identify them to various smugglers who would be picking them up after the tractor-trailer reached its destination.

“We’re certainly not stopping at looking at the driver. We’re trying to investigate and identify the different cogs, the stash houses, the other members, where the money came from,” Shane Folden, special agent in charge of U.S. Immigration and Customs Enforcement’s Homeland Security Investigations office in San Antonio, told The Associated Press.

The driver, James Matthew Bradley Jr., 60, of Clearwater, Florida, is facing charges of illegally transporting immigrants for financial gain, resulting in death. Bradley could face the death penalty. Authorities allege he drove a trailer full of immigrants from South Texas that was discovered in the parking lot of a Walmart in San Antonio early Sunday morning.

Folden said charging Bradley is just the first step in the case as investigators work to find others involved in the scheme, including those responsible for facilitating money transfers and bringing the immigrants across the border.

“The ultimate goal is to dismantle the complete organization. You don’t get there by only focusing on one aspect. You have to look at potential targets and potential related locations, both north and south,” he said.

U.S. Rep. Henry Cuellar from Texas said he was informed by law enforcement the tractor-trailer had cleared a Border Patrol checkpoint 29 miles north of the border on Interstate 35 near Laredo. Cuellar said he didn’t know whether the immigrants were loaded into the truck before or after it crossed the checkpoint.

U.S. authorities are still trying to determine how many people were inside the tractor-trailer because some fled before police arrived, Folden said.

Thirteen people who rode in the trailer remained hospitalized today in San Antonio, said ICE spokesman Greg Palmore. He declined to say how many were critical or in life-threatening condition. Officials say at least 29 people survived the smuggling attempt.

Delmin Darío López Colomo, 23, a Guatemalan survivor who remains hospitalized, said the migrants in the tractor-trailer were delivered by various different smugglers, according to Cristy Andrino, the consul of Guatemala in McAllen, Texas.

Adan Lara Vega, 27, a migrant from Mexico who survived the smuggling attempt, told the AP on Monday that they boarded the truck on a Laredo street Saturday night for the two-hour trip to San Antonio. He said the trailer was already full of people, but it was so dark he couldn’t tell how many.

At least some of the survivors are likely to become witnesses and receive consideration to remain in the United States to testify, Folden said.

It’s likely that most if not all of the survivors will be allowed to stay in the country to help authorities in their investigation, said Jeff Vaden, a former federal prosecutor who helped oversee the prosecution of a 2003 smuggling attempt in Victoria, Texas, in which 19 people died.

Many of the more than 50 immigrants who survived that attempt “were able to identify the people who harbored them or transported them or to whom they paid or spoke. That’s what enabled the government to put together the larger smuggling case above just the driver. Just like in any crime, the victims are critical witnesses,” said Vaden, who now is a partner at the Houston law firm of Bracewell LLP.

Jacob Monty, an immigration lawyer in Houston, said the help the survivors give to authorities could “lead to permanent residency.”

The driver, Bradley, remained jailed today. He had his commercial driving privileges for a truck driver suspended by Florida three months before Sunday’s deadly smuggling attempt, officials said today.

Court records show that Bradley had been cited repeatedly for violating federal motor carrier safety regulations in Iowa dating back to 1995. At least two of the tickets were for logging more hours than allowed.

Federal regulators said they are also conducting an investigation into an Iowa trucking company whose name was on the trailer. Brian Pyle, owner of Pyle Transportation, said the trailer had been sold on May 10 to an individual in Mexico and Bradley was working as an independent contractor to drive it to Brownsville, Texas, to carry out the sale.

It’s unclear what will happen to one of the migrants who died, identified as 19-year-old Frank Guisseppe Fuentes.

His parents, who live in Maryland and are in the U.S. illegally, haven’t yet told Guatemalan officials what they want done with his body, and may fear agents could come after them if they claim their son, Andrino said.