Authorities are investigating the cause of a horrific crash involving a wrong-way driver that left three people dead on the 15 Freeway in Fontana.

The crash was reported around 11:40 p.m. when a car traveling northbound in the southbound lanes collided with another vehicle just south of Sierra Avenue, the California Highway Patrol said.

A black Honda was found completely engulfed in flames with two occupants trapped inside.

An unidentified male and female were later pronounced dead, CHP Sgt. Ryan Robbe said.

A female trapped inside a maroon Kia hatchback was also killed in the crash.

Video from the scene showed the charred wreckage of the two vehicles.

“It is unfortunate when we have wrong-way drivers, especially when it’s something that’s preventable,” Robbe said.

It was unclear which car the wrong-way driver was in.

A mother who was driving her children home from Arizona told KTLA she saw headlights coming at her in the fast lane and narrowly missed getting hit. She managed to call 911 and report the incident. She also wasn’t sure which car involved the wrong-way driver.

A SigAlert was issued for the southbound 15 Freeway. All lanes were closed except for the slow lane while the CHP conducted an investigation.

The Sierra Avenue onramp was also closed.

The SigAlert was cleared and all lanes were reopened by 7:30 a.m., according to the CHP.