The Chester County coroner 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.
The 34-year-old daredevil and his passenger, 30-year-old Zachary Hartwell, died early Monday, shortly after leaving a pub in the Philadelphia suburb of West Chester. The men were in Dunn's 2007 Porsche when it careened off the road, flipped over a guardrail and crashed into the woods before bursting into flames.
The cause of the accident has not been determined, but police say speed may have been a factor. A preliminary examination of the crash site suggested that Dunn's Porsche might have been traveling more than 100 mph in the 55 mph zone.
A few hours before the 3 a.m. crash, Dunn tweeted a picture of himself drinking with Hartwell and another friend, but the photo has since been removed.
Dunn appeared on MTV shows "Jackass" and "Viva La Bam" and the three "Jackass" big-screen adaptations. Hartwell was credited as a production assistant for "Jackass Number Two."
His longtime friend and fellow "Jackass" daredevil Johnny Knoxville tweeted on Monday afternoon, "Today I lost my brother Ryan Dunn. My heart goes out to his family and his beloved Angie. RIP Ryan, I love you buddy."
Stephen "Steve-O" Glover tweeted, "I don't know what to say, except I love Ryan Dunn and I'm really going to miss him." Glover also canceled six upcoming stand-up comedy shows in Sacramento, Calif.
Meanwhile, movie critic Roger Ebert is responding to criticism over his controversial Twitter message regarding Dunn's death. Referring to the photo of Dunn drinking with friends just hours before the accident, Ebert tweeted: "Friends don't let jackasses drink and drive."
The tweet prompted a landslide of Twitter messages and Facebook posts, some profane, criticizing Ebert.
"Jackass" co-star Bam Margera fired back on Twitter, saying Ebert's response to the tragedy was insensitive. "I just lost my best friend, I have been crying hysterical for a full day," he said in a pair of angry, obscene messages.
Ebert later wrote in a Tuesday blog post, that he didn't mean to be cruel and "was probably too quick to tweet. That was unseemly."
The Associated Press contributed to this report.