Jackass daredevil Ryan Dunn had been on a drinking session with pals before the 160kph crash that killed the reality TV star and his friend.
The 34-year-old Dunn and passenger Zachary Hartwell died shortly after leaving a pub where Dunn had tweeted a photo of the pair and a third man drinking.
The photo has since been taken down.
Barnaby's of America manager Jim O'Brien said Dunn was drinking with several friends at the bar but insisted he didn't appear drunk.
A preliminary examination of the crash site suggested that Dunn's Porsche might have been travelling at more than 100mph (160kph) when it jumped a guardrail, flew into a wooded ravine, struck a tree and burst into flames.
The Chester County coroner in Pennsylvania listed blunt force trauma and thermal trauma as the official causes of death for both men.
Toxicology results will take four to six weeks to complete, coroner's office spokeswoman Patty Emmons said.
Dunn was known for making viewers cringe and snigger through vulgar stunts with his cohorts in the multimillion-dollar Jackass TV and movie franchise.
West Goshen Township police declined to discuss the ongoing investigation in detail but believe speed may have been a factor in the suburban Philadelphia crash.
Dunn's brother, Eric Dunn, said that his family was "devastated".
"We appreciate the support of Ryan's fans during this time, and we are grateful for your thoughts and prayers," he said.
"Ryan will be greatly missed, but he will forever remain in our hearts."