The entertainment news website said the single-car accident happened in Santa Clarita, Calif. TMZ said sources connected to Walker said the 40-year-old actor was in the sports car when the driver lost control and slammed into a post or a tree and caught fire.
It wasn't clear who was driving or how the accident happened, TMZ said. The name of the second occupant also was not known.
TMZ said its sources said Walker was in Santa Clarita for a car show to support the Philippines typhoon relief effort and was taking friends for rides in his new Porsche GT.
A spokesman for Walker confirmed the actor was leaving the charity event when the accident occurred, TMZ said.
Walker also appeared in "Varsity Blues," "Eight Below," "Into the Blue," "She's All That" and "Takers." His television credits included the National Geographic Channel's "Expedition Great White" series.