Authorities are investigating whether human smuggling was involved after a crash involving an SUV packed with 25 people and a lorry left 13 people dead and bodies strewn across a roadway near the US-Mexico border.

Most of the dead were Mexicans, a Mexican official said.

When police arrived, some of the passengers were trying to crawl out of the crumpled 1997 Ford Expedition while others were wandering around nearby fields.

The lorry’s front end was pushed into the SUV’s left side and two empty trailers were jackknifed behind it.

Twelve people were found dead when first responders reached the two-lane highway, which winds through fields in the agricultural southeastern corner of California about 125 miles east of San Diego.

California Highway Crash
Thirteen people have been confirmed dead following the crash (Gregory Bull/AP)

Another person died at a hospital, California Highway Patrol chief Omar Watson said.

Roberto Velasco, director of North American affairs for Mexico’s Foreign Relations Department, confirmed via his Twitter account that at least 10 of those killed have been identified as Mexicans. No identities have been released.

The cause of the collision was unclear, authorities said, and it also was not immediately known why so many people were crammed into a vehicle built to hold eight people safely.

Mr Watson said the SUV only had front seats — the middle and back seats had been removed. That would allow more people to fit into the vehicle but makes it even more unsafe.

It was not immediately clear whether the SUV was carrying migrants who had crossed the border, ferrying farmworkers to fields, or was being used for some other purpose.

California Highway Crash
A human trafficking investigation has begun in the wake of the crash (Gregory Bull/AP)

“Special agents from Homeland Security Investigations San Diego responded … and have initiated a human smuggling investigation,” the agency said in a statement, adding that other details were not being released.

Macario Mora, a spokesman for Customs and Border Protection, said agents were not pursuing the SUV at the time of the crash, which was initially rumoured. The immigration status of the passengers was unknown.

The people in the vehicle ranged in age from 15 to 53 and were a mix of males and females, officials said.

The 28-year-old driver was from Mexicali, Mexico, just across the border, and was among those killed.

The 68-year-old driver of the lorry, who is from nearby El Centro, was hospitalised with moderate injuries.

The passengers’ injuries ranged from minor to severe and included fractures and head trauma. They were being cared for at several hospitals. One person was treated at a hospital and released.

California Highway Crash
The driver of the SUV was killed in the incident (Gregory Bull/AP)

The crash occurred at an intersection just outside Holtville, which dubs itself the world’s carrot capital and is about 11 miles north of the US-Mexico border.

It was a sunny, clear morning and authorities said the lorry and its two empty containers were headed north on State Highway 115 when the SUV pulled in front of it.

A California Highway Patrol report said the SUV entered an intersection directly in front of the lorry, which hit the left side of the SUV.

Both vehicles came to a halt on a dirt shoulder.

It is not clear if the SUV ran a stop sign or had stopped before entering the highway. It is also not yet known how fast the lorry was travelling.