Actor Paul Walker, star of the Fast and Furious film series, died of the "combined effects of traumatic and thermal injuries" in a weekend car crash, the Los Angeles coroner's office announced today.

Los Angeles County coroner officials confirmed the 40-year-old and his friend Roger Rodas died in the Valencia, Calif., crash on Saturday, after their vehicle smashed into a light pole and tree before exploding into flames.

Walker, who was the passenger in the Porsche Carrera GT, died of the "combined effects of traumatic and thermal injuries," while driver Rodas died of "multiple traumatic injuries," the autopsy report says.

Investigators are still probing what exactly caused Rodas to lose control, but have said speed was a factor.

According to witnesses, Walker and Rodas had been attending an event for the actor's charitable organization Reach Out Worldwide when they decided to take the car for a brief test drive.

Detectives continue to gather evidence and investigate the cause of the crash, including poring over surveillance video from the area. The remains of the Porsche have been moved to a Sheriff's department impound yard. Fans continue to flock to the site daily to mourn the star, according to police officials.

Walker starred in all but one of the six Fast and Furious films, the lucrative franchise that had been set to release a fresh instalment next July. On Wednesday, Universal Pictures announced it has shut down production on the upcoming release indefinitely.

Fast & Furious 7 will shut down "for a period of time so we can assess all options available to move forward with the franchise," the studio said.

The latest instalment of the racing series had begun shooting in September and was on a fast track for release next summer. Cast and crew were on a break for the U.S. Thanksgiving last weekend. Though much has been filmed, it's far from complete.

"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 filmmakers," the studio said.

The circumstances of Walker's death — a fiery car crash in a specialty sports car — are so reminiscent of the franchise that made him famous that many feel the next movie will be under intense scrutiny for its portrayal of the fatal risks of street racing.

The studio had previously announced that it will donate a portion of the proceeds from the upcoming DVD, Blu-ray and digital release of Fast & Furious 6 to Walker's charity.

Producers of another of Walker's films, the Hurricane Katrina drama Hours, announced this week they would release the movie as planned on Dec. 13.

Set in the aftermath of Hurricane Katrina, Hours features Walker as the father of an ill newborn cut off from the world when the storm hits and the hospital is evacuated. The film, which he also co-produced, is said to showcase Walker's dramatic acting talent.

Relativity also said it plans to release Walker's film Brick Mansions, a remake of the French action film District B13, early next year.