A post-mortem shows Fast & Furious star Paul Walker was killed in a car crash by the combined effects of the impact and subsequent fire.

Walker, a passenger in the car driven by his friend and financial adviser Roger Rodas, died on Saturday when the 2005 Porsche Carrera GT smashed into a lamppost and tree and then exploded in flames.

The Los Angeles County coroner’s office released the post-mortem results on Wednesday. The report also says Rodas was killed by the impact.

Walker starred in all but one of the six Fast & Furious blockbuster films that glorified fast cars and dangerous driving.

Sheriff’s investigators are still trying to determine exactly what caused Rodas to careen out of control. They have said speed was a factor.

Universal Pictures announced it has shut down production on Fast & Furious 7 indefinitely following the death of Walker.

The studio said the film will shut down “for a period of time so we can assess all options available to move forward with the franchise”.

The seventh instalment of the street racing series had begun shooting in September. While much of Fast & Furious 7 has been filmed, it’s far from complete.

When Walker died in the crash the film was on break for the Thanksgiving holiday. Shooting had been planned to resume on Monday in Atlanta, but production was put on hold following Walker’s death.

Universal had been trying to fast-track Fast & Furious 7 for a July 11 release, a date that’s now likely to be postponed. Universal hasn’t yet announced any release date change.

“Right now, all of us at Universal are dedicated to providing support to Paul’s immediate family and our extended Fast & Furious family of cast, crew and film-makers,” the studio said in a statement.