Los Angeles County sheriff's officials said speed played a factor in the Saturday crash in Santa Clarita but have not said how fast they believe the car was going. It's unclear when the probe will be concluded.
"The investigation of the traffic collision is ongoing," the department said in a press release. "This includes examination of the wrecked vehicle for any further evidence that could help investigators to determine the cause of the collision."
The sheriff's department alleges that two men stole the T-top roof panel of the Porsche after the crash.
The department announced Thursday that one man was in custody and that another suspect was expected to surrender to detectives soon.
One suspect, 18-year-old Jameson Witty, was arrested on suspicion of grand theft and tampering with evidence. He was being held on $20,000 bail, officials said.
In a news release, the sheriff's department said the alleged theft occurred while the Porsche was being towed away.
"A witness saw a male exit a vehicle that was following the tow truck. The male grabbed a piece of the wrecked Porsche off the tow truck bed. The male drove away with the stolen vehicle part. The tow truck driver reported the theft to the Santa Clarita Valley Sheriff’s Station," the statement said.
Search warrants were served, and the sheriff's department found some of the parts at a home in Canyon Country.
Walker, 40, died Saturday from a combination of traumatic injuries and burns after the Porsche Carrera GT he was riding in crashed into a light pole in Santa Clarita and erupted in flames, the Los Angeles County coroner's office said Wednesday.
Roger Rodas, 38, Walker's financial advisor and friend, was behind the wheel of the high-performance 2005 Porsche when it crashed. He was killed by the impact alone, a medical examiner concluded.
Since the crash, a fans' memorial has taken over the crash site and a massive tribute drive is planned in Walker's honor. Walker had made enough money that he kept a warehouse full of prized vehicles and later opened a business, Always Evolving, that customized and sold high-performance cars -- earning a place in the hearts and minds of car enthusiasts.
The footage in the tribute video is short on dialogue but does feature a line by Vin Diesel's character, with most of the cast gathered around: “The most important thing in life will be the people in this room, right here, right now.”
When Walker died, the cast of "Fast & Furious 7" was on a brief Thanksgiving break from filming in Atlanta. Universal Pictures on Wednesday officially put the film on hiatus.
"Right now, all of us at Universal are dedicated to providing support to Paul's immediate family and our extended 'Fast & Furious' family of cast, crew and filmmakers," the studio said. "At this time we feel it is our responsibility to shut down production on 'Fast & Furious 7' for a period of time so we can assess all options available to move forward with the franchise."
The studio also announced this week that it would donate a percentage of proceeds from the home entertainment sales of "Fast & Furious 6" to Walker's charity, Reach Out Worldwide. Walker and Rodas had attended a fundraiser for the nonprofit just before the crash.