Walker, 40, was the passenger in a 2005 Porsche driven by financial adviser Roger Rodas, 38, that crashed and then erupted in flames after striking a light pole and tree.
The coroner's office told ABC News that two different doctors did autopsies on the two men. They found that Rodas died on impact, with Walker dying "maybe" a few seconds after from the combined effects of the impact and the fire.
"Both deaths have been ruled by the coroner to be accidents," the report adds.
The report confirms that the two men who died in the vehicle were in fact Walker and Rodas, after reports earlier in the week that dental records were needed to identify the deceased.
Toxicology reports are expected in six to eight weeks.
Los Angeles County Sheriff's investigators are still trying to determine the cause of Saturday's crash, which claimed the life of the "Fast & Furious" star and his friend. They have said speed was a factor.
Sheriff's detective Jeff Maag told People magazine the driver "was doing well over 45 [mph] – [it's] fair to say at least twice that."
That means Maag believes Rodas was going at least 90 mph on a street where the limit was just 45.
He added it will take days or weeks to complete the investigation and conclude how fast the car was going and whether mechanical problems caused the crash.