The victims of Tuesday’s deadly crash in rural California probably were undocumented immigrants who had crossed the border illegally during a smuggling attempt minutes before the collision, according to U.S. Customs and Border Protection officials.

Minutes before California Highway Patrol troopers responded to the grisly crash, which killed at least 13 people, El Centro Sector Border Patrol agents reported that two vehicles had driven from Mexico through a 10-foot breach in the border fence 30 miles away off Interstate 8 in Imperial County.

The first to breach the fence was a large Chevrolet sport utility vehicle that was later found engulfed in flames about 6:06 a.m., according to a CBP statement. Agents found 19 people hiding in the nearby brush, and they were taken into custody.

The second was a maroon Ford Expedition carrying 25 passengers that drove into the path of a large truck on State Road 115 on Tuesday. Surveillance footage confirms that the Ford Expedition was the same SUV that collided with the truck about 6:15 a.m., killing at least half the occupants, including the 28-year-old driver.

Border Patrol’s special trauma and rescue team responded to the crash to administer help to the victims.

“Human smugglers have proven time and again they have little regard for human life,” El Centro Sector Chief Gregory Bovino said in a statement. “Those who may be contemplating crossing the border illegally should pause to think of the dangers that all too often end in tragedy.”

The Border Patrol is investigating what it has called a smuggling attempt.