The 13 people killed in one of the deadliest highway crashes involving migrants sneaking into the US had entered California through a section of border fence with Mexico that was cut away, apparently by smugglers, immigration officials have said.

Surveillance video showed a Ford Expedition and Chevrolet Suburban drive through the opening early on Tuesday, said Gregory Bovino, the Border Patrol’s El Centro sector chief.

The video has not been publicly released as it is part of an ongoing investigation.

California-Highway Crash
Workers mending the fence on Wednesday (Eugene Garcia/AP)

The Suburban, carrying 19 people, caught fire for unknown reasons on a nearby interstate highway after entering the US. All escaped the vehicle and were taken into custody by Border Patrol agents.

The Expedition crammed with 25 people continued on, and a tractor-trailer struck it a short time later. Ten of the 13 killed in that crash have been identified as Mexican citizens. The Border Patrol said its agents were not pursuing the vehicle before the wreck.

The opening in the fence was some 30 miles east of the crash in the heart of California’s Imperial Valley, a major farming region now at the height of a harvest that provides large amounts of vegetables to US supermarkets.

California Highway Crash
The scene of the crash in which 13 people in the SUV were killed (Gregory Bull/AP)

It was made of steel bollards that were built before former President Donald Trump blanketed much of the border with taller barriers that go deeper into the ground.

Photos show a panel of eight steel poles was lifted out and left on the ground in the desert next to an old tire and other debris.

“Human smugglers have proven time and again they have little regard for human life,” Mr Bovino said.

“Those who may be contemplating crossing the border illegally should pause to think of the dangers that all too often end in tragedy, tragedies our Border Patrol Agents and first responders are unfortunately very familiar with.”