'Jackass' star Ryan Dunn's death was so violent it is unknown if it was caused by the car crash or the subsequent fire.

The autopsy result for the actor and Zachary Hartwell - who was also killed when Ryan's Porsche flew over a barrier and into a tree on Route 332 yesterday (20.06.11) - were both dead when officers arrived on the scene, and according to TMZ.com the Chester County Coroner has confirmed it is impossible to determine how they died.

Toxicology results will determine the role alcohol played in the accident but will not be revealed for at least four weeks, but he did post pictures hours before the accident of him enjoying himself in a bar.

Van Toffler, president of MTV Networks, has paid tribute to the star, noting the 'Jackass' "brotherhood" would not be the same as a result of his passing.

He said: "We are devastated by the tragic loss of Ryan Dunn - a beloved member of the MTV family for more than a decade.

"The 'Jackass' brotherhood will never be the same."