Investigators Reveal Cause of Crash That Killed Jessi Combs

Investigators say wheel failure at speeds approaching 550mph caused the crash that killed "the fastest woman on four wheels." Professional racer and Mythbusters cast member Jessi Combs, 39, died on Aug. 27 while driving a 52,000 horsepower North American Eagle jet car across a dry lake bed in Oregon's Alvord Desert. The Harney County Sheriff's Office said Tuesday that investigators determined there was apparently "a mechanical failure of the front wheel, most likely caused from striking an object on the desert," USA Today reports. "The front wheel failure led to the front wheel assembly collapsing," the sheriff's office said.

Combs' cause of death was "blunt force trauma to the head occurring prior to the fire that engulfed the race vehicle after the crash," the sheriff's office said. The North American Race Team says the vehicle's wheels were designed to retain their integrity at speeds up to 900mph, Fox reports. Combs had been trying to beat the 398mph women's four-wheel land speed record she set in 2013 as well as the 512mph women's land speed record set by Kitty O'Neil in a three-wheeled rocket car in 1976. The team says Combs—who was driving in the same location as O'Neil—achieved two runs at 531.889mph before the crash. The team hopes to get the record approved by the Guinness Book of World Records. (More auto racing stories.)