Toyota Motor Corp. said Monday it believes the driver of a Prius involved in a high-speed incident on a California highway repeatedly pressed the brake and accelerator, apparently defeating a system that can prevent unintended acceleration, The Wall Street Journal reported.

The driver, James Sikes, has said he applied heavy pressure to the brake pedal while the car accelerated on its own last week near San Diego. Toyota said the condition of the car's brakes and information captured by the vehicle's diagnostic system don't support that version of events—even as the California Highway Patrol challenged Toyota's view.

"We believe the vehicle was being driven with the front brakes lightly applied," Bob Waltz, Toyota's U.S. vice president for product, quality and service support, said at a press conference in San Diego.

Sikes' attorney, John Gomez, said he would have no further comment until the National Highway Traffic Safety Administration completes its own investigation. NHTSA examined the Prius last week alongside Toyota's investigators.

Toyota's Waltz said data from the onboard computers indicate the brakes and accelerator were depressed about 250 times during the incident.

Toyota spokesman Mike Michels said a system that can stop the car if both gas and brake pedals are pressed at once won't be triggered if the brakes are only lightly pressed. In this case, the brakes would have to be released repeatedly to maintain a high speed without triggering the system.

"So the on-and-off action would have been required to keep the car going at any kind of high speed," Michels said.

California Highway Patrol spokesman Brian Pennings said there are "some serious discrepancies between what Toyota is saying and what our officer's observations are. The CHP intends to release its incident report with more details shortly.

While the incident was occurring, an officer who pulled up beside Mr. Sikes's car said he saw the driver appear to lean back, lift his body off his seat and push his feet on the brake pedal. CHP officers also said they saw plumes of smoke from the car and brake dust on the wheels, which they believed had come from heavy brake use.