Speed caused the car crash that killed Paul Walker late last year.
The 'Fast and the Furious' actor perished alongside his friend Roger Rodas, who was driving when the Porsche Carrera GT they were travelling in lost control and crashed in Santa Clarita, California on November 30, and investigators have reportedly found no evidence of mechanical failure.
A source told gossip website TMZ.com that Roger was driving between 81 and 94 MPH when he lost control going around a curve and smashed into a light pole, which had a speed limit sign of 45 MPH, before the vehicle burst into flames.
Another insider from the Los Angeles County Sheriff's Department said that the agency that conducted the mechanics analysis had concluded in their report, which has yet to be officially released, that excessive speed triggered the fatal accident.
During the investigation, Porsche mechanics flew to LA from Germany to examine the car's brakes, engine, body and a tire that wasn't destroyed in the fire.
Shortly before the accident, Paul, 40, and Roger took part in a car show, organised to raise funds for victims of a typhoon in the Philippines and tornado in Indiana.
Eyewitness Jim Torp, who attended the event, said at the time that he did not think the duo were driving dangerously.
He said: "Roger was definitely behind the wheel. Roger slowly drove it out - he didn't take off recklessly. There were children around, after all. They were only gone for five or ten minutes and never came back."
He added: "It was clear the car had hit two trees then finally hit a street lamppost. Parts of the car were strewn everywhere on the street, as far as 150 feet. I didn't see any skid marks. Where the car had crashed was on a long straightaway. How fast they were going, I don't know.
"Roger was not a reckless guy. He was a family man. He has a wife and two young children. He never did anything careless."