IMPERIAL COUNTY, Calif. (NewsNation Now) — Authorities are investigating whether human smuggling was involved in the Tuesday morning collision that killed at least 13 after a semitruck crashed into a SUV carrying 25 people on a Southern California highway near the U.S.-Mexico border.

U.S. Immigration and Customs Enforcement said late Tuesday that agents in its Homeland Security Investigations unit “have initiated a human smuggling investigation (into Tuesday’s crash). The investigation is ongoing and no further details are available at this time.”

The Mexican government said 10 of the dead were Mexican citizens and the nationalities of the three others who died was undetermined.

California Highway Patrol Chief Omar Watson said 12 people died at the scene just outside of Holtville, California, which is about 11 miles north of the U.S.-Mexico border. Another person died after arriving at the hospital. Hospital officials earlier reported there 15 people were killed in the crash and that more people were inside the SUV.

“It was a pretty chaotic scene,” Watson said, who also described it as “a very sad situation.”

California Highway Patrol Officer Jake Sanchez said the SUV was a 1997 Ford Expedition that would typically seat eight to nine people legally. He said the SUV had stopped at an intersection and then drove “directly in the path of the big rig” just after 6 a.m. PST. The tractor-trailer full of gravel struck the left side of the SUV, which appeared to have been pushed off the road.

The 22-year-old driver of the Ford Expedition was from Mexicali, Mexico, and was killed. The 69-year-old driver of the big rig, who is from nearby El Centro, was hospitalized with moderate injuries.

The crash occurred at an intersection just outside the agricultural community of Holtville, which dubs itself the world’s carrot capital.

Authorities said the tractor-trailer and its two empty containers were northbound on State Highway 115 when the SUV pulled in front of it from Norrish Road. It’s not clear if the SUV ran a stop sign or had stopped before entering the highway. It’s not yet known how fast the tractor-trailer was traveling.

Seats of the 1997 Ford Expedition were removed except for the driver and right front passenger’s, said Watson. Multiple people were ejected from the vehicle, according to CHP. The ages of the victims ranged from 16 to 55.

Watson described a grisly scene outside Holtville, a rural town about 11 miles north of the border with farms that grow vegetables and alfalfa for cattle feed. Officers arrived to find that some people had been ejected from the SUV onto the ground. Some of the passengers had pulled themselves from the wreckage, and others who were injured were wandering around.

Multiple SUV passengers were flown or sent to hospitals for injuries that included fractures and head trauma. Four were flown to Desert Regional Medical Center in Palm Springs, where three were in intensive care, spokesman Todd Burke said.

A 1997 Ford Expedition can carry a maximum payload of 2,000 pounds. If it had 25 people inside, that would exceed the payload limit — which would tax the brakes and make it tougher to steer, said Frank Borris, former head of the U.S. 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,” said Borris, who now runs a safety consulting business.

SUVs of that age tended to be top-heavy even without carrying a lot of weight, Borris said.

“With all of that payload above the vehicle’s center of gravity, it’s going to make it even more unstable,” he said.

Macario Mora, a spokesman for Customs and Border Protection in Yuma and El Centro, said the Border Patrol helped other law enforcement with the crash. He said the immigration status of those in the vehicle was unknown and being investigated.

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

A harvest is underway in the region of most of the winter lettuce and other leafy greens eaten in the United States.

Officials from the Holtville and Imperial County fire departments and the California Highway Patrol spokesperson for the area could not immediately be reached.

The area is about two hours east of San Diego. Imperial County is the least populous county in California, with 180,000 residents.

The Associated Press contributed to this story.