Story highlights Drugs, alcohol, mechanical trouble, racing were not involved in Paul Walker's crash

Walker's Porsche was speeding "between 80 and 93 mph" when it wrecked last year

Investigation report clears up lingering questions about the star's death

Walker and Roger Rodas wore seat belts and airbags deployed in the Porsche

Speed killed "Fast & Furious" star Paul Walker, according to the investigation of the fiery car crash that ended the actor's life last year.

"Investigators determined the cause of the fatal solo-vehicle collision was unsafe speed for the roadway conditions," Los Angeles County Sheriff's Commander Mike Parker said Tuesday.

The high-performance 2005 Porsche Carrera GT was going "between 80 and 93 mph at the time the car impacted a power pole and several trees," the final report said. The posted speed limit on the Santa Clarita, California, office park road was 45 mph.

The sheriff's conclusion is no surprise, since the coroner's report previously estimated the car was speeding at 100 mph . But the investigative report does clear up some questions that have lingered about how Walker died.

Walker, 40, and friend Roger Rodas , 38, had no drugs or alcohol in their blood. Both men were wearing seat belts. The airbags deployed as they should have when the car clipped a light pole and several trees, investigators said.

Nothing mechanical went wrong to cause their Porsche to leave the wide road. Investigators found "no pre-existing conditions that would have caused this collision," the report said. Experts from Porsche and Michelin were consulted.

The car did have "an aftermarket exhaust system" that helped it go faster, the report said. The tires on the car, which was mostly displayed in a showroom and rarely driven, were more than nine years old.

One early theory -- considering the nature of Walker's movies -- that he and Rodas could have been racing another car was not supported, the report said.

"No eyewitness contacted the Los Angeles County Sheriff's Department to say there was a second vehicle and there is no evidence to indicate there was a second car involved in the collision," it said. Video recorded by several security cameras on nearby buildings "helped skilled investigators to determine the cause of the collision and that no speed contest was taking place."

The Los Angeles County coroner's office released a15-page report in January that concluded the two men apparently did not live long after the crash.

Walker and Rodas, racing team partners, left a charity event at a car shop co-owned by the men to take a ride in an office park in the community of Valencia in Santa Clarita, about 30 miles north of Hollywood. The crash happened a few hundred yards away on a wide street.

The autopsy revealed "scant soot" in Walker's trachea, suggesting his life ended before the smoke and fire engulfed the car.

The actor's body was badly burned "and in a pugilistic stance. His right wrist was fractured and his left arm was fractured," the report said. Rodas was also described as in "a pugilistic" -- or defensive -- position.

Walker suffered fractures of his left jawbone, collarbone, pelvis, ribs and spine, the report said.

Rodas "rapidly died of severe blunt head, neck and chest trauma," the report said.