The report, released by the Los Angeles County Coroner's Office on Friday, states that on Nov. 30, Walker's friend, Roger Rodas, was driving the red Porsche Carrera GT at an unsafe speed, estimated by witnesses to be 100 mph or more.
"For unknown reasons, the driver lost control of his vehicle, and the vehicle partially spun around, and began traveling in a southeast direction," the report states.
The Porsche then hit a curb, and the driver's side of the vehicle slammed into a tree and a light post. The force of the collision caused the Porsche to spin 180 degrees and continue in an easterly direction. The report states that the "passenger side of the vehicle then struck another tree and burst into flames."
No alcohol or drugs were found in Walker's or Rodas' system, according to the report.
The deaths were ruled accidents. Walker died from combined effects of traumatic and thermal injuries, while Rodas died as a result of multiple traumatic injuries.
Also on Friday, two men accused of stealing parts from the wrecked Porsche appeared in court. Anthony Edward Janow, 25, and James Brooks Witty, 18, pleaded not guilty to felony counts of grand theft and misdemeanor counts of destroying evidence and resisting or obstructing a peace officer.
Both men are due to return to court Feb. 25 for a preliminary hearing setting date.