U.S. Immigration and Customs Enforcement announced Tuesday that agents are conducting a human smuggling investigation and were at the scene of a devastating crash in California that left at least 13 people dead, according to the agency.

The investigation was announced after human smugglers and 25 illegal immigrants jammed into a single SUV, which collided with a big rig and left bodies scattered across a roadway near the U.S. Mexico border on Tuesday.

“Special agents from Homeland Security Investigations San Diego responded … and have initiated a human smuggling investigation,” ICE said in a statement. Police arrived to find some of the passengers trying to crawl out of the crumpled 1997 Ford Expedition- which normally seats eight- while others were wandering around the nearby fields. Officials added that the SUV’s back seats were removed to create more space for passengers.

California Highway Patrol (CHP) officers found 12 people dead at the scene. Another person died at a local hospital, authorities said. The remaining eight victims with injuries were transported to local hospitals. “It was a pretty chaotic scene,” said CHP Chief Omar Watson.

Mexican consulate personnel confirmed that at least 10 of the people killed in the crash were Mexicans, according to a tweet from Roberto Velasco, director of North American affairs for Mexico’s Foreign Relations Department.

Those in the vehicle ranged from 15 to 53 years old, officials said. Authorities are still working to confirm the nationality of three individuals. “We will continue in close collaboration with the authorities in order to assist the deceased and injured Mexican people,” Velasco added.

The collision occurred at an intersection just outside Holtville, Calif., about 11 miles north of the U.S.-Mexico border, authorities said. Customs and Border Protection (CBP) that the crash happened after a hole was cut in the border fence near Calexico, Calif.

The area is known for smuggling. Migrants who died after crossing the border are buried in unmarked graves in Holtville’s cemetery at the edge of town.

As of early Wednesday, the immigration status of all the passengers was unknown, authorities said. Macario Mora, a spokesman for CBP noted that agents were not pursuing the SUV at the time of the crash.

Dr. Adolphe Edward, chief medical officer at El Centro Regional Medical Center, said at the hospital’s news conference that they “don’t use the term undocumented in the hospitals.”  “To us, these folks that came to us are patients,” he added.

The Ford Expedition reportedly entered an intersection directly in front of the big-rig before hitting the left side of the SUV which appeared to have been pushed off the road, according to the CHP. Both vehicles came to a halt on a dirt shoulder.

Authorities do not yet know if the driver of the SUV stopped at a stop sign before crossing into the path of the big rig around 6:15 a.m., Watson told reporters. It was also not immediately known why so many people were crammed into a vehicle built to hold eight people.

“It was an unusual number of people in an SUV, but we don’t know who they were,” said Mora.

If 25 people were inside the 1997 Ford Expedition, it would have easily exceeded the maximum payload limit of 2,000 pounds, said Frank Borris, former head of the National Highway Traffic Safety Administration’s Office of Defects Investigation.

“You’re going to have extended stopping distances, delayed reactions to steering inputs, and potential over-reaction to any type of high-speed lane change,” Borris added.

The 28-year-old SUV driver- from Mexicali, Mexico- was among those killed. The 68-year-old driver of the big rig, who is from nearby El Centro, was hospitalized with moderate injuries.