Federal officials are sending an investigator to determine what caused a Toyota Prius to race out of control on a California freeway.

A spokeswoman for the U.S. Department of Transportation said Tuesday that the National Highway Traffic Safety Administration will try to determine the cause of the incident in San Diego County.

Driver James Sikes sped along Interstate 8 for 20 minutes Monday before a Highway Patrol officer helped slow down the car.

CHP Officer Brian Pennings says the 2008 Prius was towed to a Toyota dealership in El Cajon — presumably for inspection.

The incident took place the same day that Toyota held a demonstration to challenge claims that car electronics could cause the gas pedal to stick. Toyota has recalled millions of cars but claims the problems are simply mechanical.