ANTIOCH -- A driver injured over the weekend in what one Antioch Speedway official described as the most serious sprint-car wreck at the dirt track in several years suffered a traumatic brain injury and compressed vertebrae, according to the organization that runs the race series.

An updated Facebook page for the Golden State King of the West Series posted that driver Peter Murphy was diagnosed initially with a concussion, but his body began to show more severe symptoms than just a concussion later Saturday night.

A nursing supervisor at John Muir Medical Center in Walnut Creek, where Murphy was taken after the Saturday night wreck, said he remained in "stable but serious condition" Tuesday morning.

Doctors also found severe stretching and swelling in Murphy's tendons around his neck, according to the post.

Murphy was injured when his compact winged car rolled over during lap 14 of a 30-lap race. He remained trapped in the wreckage for about 40 minutes after the wreck, which happened when Murphy approached slower traffic, clipped the right rear wheel of a car in front of him and flipped.

A second car struck the underside of Murphy's car as it sat on its side.

John Soares Jr., Antioch Speedway's owner/promoter for the past 17 years, said the wreck involving the veteran from Australia was as bad as he can remember.

"It was probably one of the most serious (crashes) since I've been here," he said. "Thank God it was a winged car; (the wings) absorbed a lot of the impact."

Gary Thomas, a spokesman for the sprint car series, added that the crash was the worst in a dozen races on the circuit this year throughout Northern California and Nevada.

Paul Burgarino contributed to this story. Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.