Walker, 40, was a passenger in a Porsche sports automobile driven by a mate - who also died - when it crashed north of Los Angeles.
Walker was said to be attending a charity event at the time.
Walker also starred in the suspense drama Hours, a film that is set for release this month.
They starred in all but of the films in the Speedy & Enraged franchise, the sixth of which opened in May.
The Los Angeles County Sheriff's department said the crash happened in the community of Valencia.
Los Angeles (CNN) -- "Fast & Furious" star Paul Walker may have initially survived a horrific automobile crash but died moments later due to a combination of injuries from the impact and the resulting fire, according to a coroner's document.
The one-page initial document released by the Los Angeles County coroner's office Wednesday listed the reason for the actor's death as the "combined effects of traumatic and thermal injuries."
An post-mortem concluded that Roger Rodas, who was driving the red Porsche Carerra GT, suffered "multiple traumatic injuries," but it was not clear in the document if they was still alive when the automobile burst in to flames soon after the wreck.
Since different doctors did the separate autopsies, the difference in the description of their injuries does not mean there deaths were significantly different, Los Angeles
It is not known how long each man lived after the crash as the fire began, Winter said. That information may be included when full post-mortem reports are released in several weeks, they said.
Actor Paul Walker dies
The coroner confirmed what lots of witnesses told investigators: Rodas was the driver in the crash; Walker was the passenger of the high-performance Porsche that clipped a light pole as well as a tree before erupting in flames on a Southern California street Saturday afternoon.
