Santa Clarita, California (CNN) -- Drag racing may have been involved in the fiery crash that killed "Fast & Furious" actor Paul Walker on Saturday, an investigator said Monday.

Investigators got a phone call tip Sunday suggesting that another car was at the scene when the 2005 Porsche Carrera GT, driven by Walker's racing team partner, slammed into a light pole and burst into flames, Los Angeles County Sheriff's Sgt. Richard Cohen told CNN.

"Naturally, from an investigative standpoint, we need to find out if that is one of the issues," he said.

Even if drag racing was not involved, investigators are looking at the possibility that another car veered in front of the Porsche and caused the crash, Cohen said.
Actor Paul Walker dies Actor Paul Walker dies
Witness: Walker was not drag racing
View scene of Walker's deadly car crash

Jim Torp, a car enthusiast who was at the charity event that Walker attended before the wreck, said he doubted drag racing was involved. Walker was smiling as he got into the Porsche minutes earlier.

Torp thought he heard a blast in the distance before the car slammed into a light pole, he said.

"What the first explosion was, I don't know if their tire blew up, because it sounded like a tire blew on the car," Torp told CNN Monday.

Tire skid marks on the asphalt near the crash site, which indicate a car was doing doughnut spins, also are being looked at, Cohen said. It has not been concluded that they are related to the Walker wreck, he said. The street has a reputation for fast drivers, which spurred a crackdown by deputies two years ago, he said.

Torp told CNN that he looked closely at the skid marks and concluded they were left by a car with smaller tires.

Walker and Roger Rodas, who was believed to be driving, died in the wreck on Hercules Street, a wide business park road, in the community of Valencia inside