El CENTRO, Calif. (AP) — An SUV believed to be carrying 27 people crashed into a semitruck Tuesday on a Southern California highway, killing 15 people and leaving others injured, hospital officials said.

Judy Cruz, director of El Centro Regional Medical Center’s emergency department, said 14 people died at the scene, which is about 11 miles (18 kilometers) north of the U.S.-Mexico border, and another died after arriving at the hospital.

Officials believe there were 27 people in an SUV that struck a tractor-trailer full of gravel. Multiple patients were sent to hospitals for their injuries, including four flown to Desert Regional Medical Center in Palm Springs, spokesman Todd Burke said. Three were in intensive care, he said.

“The patients are, of course, going through a little bit of a difficult time, as you can imagine,” said Dr. Adolphe Edward, the El Centro hospital’s chief executive officer.

It was not immediately clear what caused the crash in the agricultural southeastern corner of California on a highway running through fields about 100 miles (160 kilometers) east of San Diego.

Macario Mora, a spokesman for Customs and Border Protection in Yuma and El Centro, said the Border Patrol was helping 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, as well as the California Highway Patrol spokesperson for the area, could not immediately be reached.

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