A fatal SUV crash in southern California Tuesday that killed at least 13 people may be tied to a border wall breach by migrants entering the U.S. from Mexico, a U.S. official told The Associated Press Wednesday. 

The official, whom the AP reported had direct knowledge of the investigation, said that investigators believe that migrants had breached a border wall before an SUV carrying 25 people collided with a tractor-trailer along State Route 115 in Holtville, Calif., not far from the Mexican border. 

According to the AP, the official, who spoke on the condition of anonymity because they were not authorized to speak publicly, added that investigators are also looking into other migrants who reportedly crossed the border at the same time in an alleged smuggling operation. 

The AP noted that the other migrants were not in the vehicle that later crashed. 

U.S. Immigration and Customs Enforcement announced late Tuesday that its homeland security investigations unit had “initiated a human smuggling investigation,” into Tuesday’s fatal crash. 

“The investigation is ongoing and no further details are available at this time,” the agency added in a statement, the AP reported. 

The reported investigation into a border wall breach comes after El Centro Regional Medical Center CEO Adolphe Edward told The New York Times Tuesday that he thought the victims were undocumented migrants.

Edward later added in a press conference, "We don't use the term undocumented in the hospitals.” 

"To us, these folks who came to us are patients,” he said. 

Authorities said the cause of the crash was not yet known as of Wednesday, though they noted that the 1997 Ford Expedition involved in the crash is built to hold only eight people safely. 

Omar Watson, chief of the California Highway Patrol’s (CHP) border division, said that all the seats except for those for the driver and front passenger had been removed from the car. 

The Mexican government said 10 of those killed in the crash were citizens of Mexico, according to the AP. The nationalities of the other three victims are not yet known. 

There was initially confusion Tuesday on the total death count, with officials at El Centro Medical Center announcing that 15 people had died, with 14 people found dead at the scene and another person dying upon arrival to the hospital.

CHP later reported at least 13 fatalities, with 12 confirmed deaths at the scene of the crash.