Investigators are trying to determine the exact speed of the red Porsche Carrera GT which crashed in Los Angeles killing Fast & Furious star Paul Walker and his friend Roger Rodas, a former racing driver. Walker was believed to have been a passenger in the car.

Officials in the Los Angeles County Sheriff's Department investigating the case have, however, confirmed that speed was a contributing factor in the crash, according to the Associated Press. The sports car was the only vehicle involved in the accident.

As soon as the Porsche hit a tree and a lamppost, it exploded into flames, according to eyewitness accounts. Authorities found the car engulfed in flames when they arrived at the scene of the crash.

"When I went out there, it was just smoke. Just black smoke. I thought it was a brush fire," Alyssa Yorton, a resident in the locality, told the Los Angeles Daily News.

The street had a speed limit of 45mph and officials say it will take time to determine the exact speed of Walker's car at the time of crash.

"It [the car] was engulfed in flames. There was nothing. They were trapped," Antonio Holmes, who said he was Walker's friend, told the Santa Clarita Valley Signal.

Local reports suggest parts from the crashing car damaged a window in a nearby building.

However, authorities have not officially released the names of the duo died in the crash. The autopsy of the bodies has reportedly been kept in abeyance as they have been charred beyond recognition.

The authorities are said to be waiting for the dental records of Walker and his friend in a bid to identify the bodies.