US safety regulators and car-manufacturer Toyota are investigating the circumstances surrounding a Prius car that sped out of control on a California freeway earlier this week.
US transportation secretary Ray LaHood said two investigators from the National Highway Traffic Safety Administration were sent to San Diego "to be part of the investigation" of Monday's incident, which left the driver of a runaway car rattled but unhurt.
"NHTSA is reminding owners of all recalled vehicles to contact their dealers immediately if they are experiencing problems," NHTSA spokeswoman Olivia Alair said in a statement.
Toyota Motor Corp said its own inspectors were working to try to find out what caused the 2008 Prius to surge uncontrollably to 150km/h (94mph) as it was being driven by its owner, James Sikes (61).
The incident, involving a dramatic pursuit by a highway patrol car, came at a bad time for Toyota, which has struggled in recent weeks to reassure a jittery public it has turned a corner in dealing with safety issues that sparked a recall of 8.5 million vehicles worldwide.
Seven weeks into the crisis, Toyota has begun trying to reverse a slump in its new car sales by offering buyers aggressive discounts.
Just hours before news broke of the San Diego mishap, Toyota held a news conference seeking to discredit an external study critical of its computerised safety systems and denying again the existence of a flaw in its electronic engine throttles that could cause sudden, unintended acceleration.
Adding to Toyota's woes, the company said it was expanding a repair campaign for 2002-2003 model Tundra pickup trucks.
Separately, the Japanese automaker asked a Michigan appeals court to intervene to keep its top two US executives from being questioned under oath by lawyers for the family of a woman killed while driving a Camry in 2008.
Toyota has insisted that cases of unintended acceleration, when not caused by human error, were rooted in mechanical problems - namely ill-fitting floor mats, a sticky accelerator pedal, or both, although some motorists have reported the problem after going through with repairs.
Mr Sikes told police his car surged out of control when he deliberately accelerated to pass another vehicle on the road and the engine seemingly jolted into higher speed by itself.
"I pushed the gas pedal to pass a car and it did something kind of funny," Mr Sikes told reporters. "It jumped and it just stuck there. As it was going, I was trying the brakes ... It wasn't stopping."
California Highway Patrol spokesman Brian Pennings said police have no reason to doubt Mr Sikes' account, based on officers' own observations and evidence of heavy brake use.
"There was heavy brake dust on the inside of the wheels and the brakes were smoking when the officer finally caught up to him," Mr Pennings said.
He said Mr Sikes also appeared genuinely shaken by the incident and complained of chest pains, prompting police to call paramedics, who evaluated him at the scene and managed to calm him down without taking him to the hospital.
Because there was no crash or injuries, the highway patrol did not conduct its own inspection of the car, he said.
The Prius has been a "halo" car for the world's largest car manufacturer and dominates the market for fuel-efficient hybrid vehicles, though 2004-2009 models were recalled due to concerns that loose floor mats could entrap the accelerator pedal.
Mr Sikes told reporters he received a recall notice for his Prius and brought it into a dealership, but was turned away and told the vehicle was not on recall lists.
Mr Sikes' brush with unintended acceleration lasted about 20 minutes and covered about 30 miles of freeway at high speeds before he managed to regain control of his car.
A highway patrol officer sent to assist Mr Sikes after he called emergency dispatchers pulled alongside the Prius and used his loudspeaker to tell him to apply foot brakes and the emergency brakes together and turn off the engine.
Once the Prius slowed to around 80km/h (50mph), he turned off the ignition and the car rolled to a stop with the trooper's car in front of it.
Monday's incident, which attracted widespread media coverage, occurred a short distance away from the site of a similar incident in August 2009 that ended in a fiery crash of a Lexus sedan, killing the off-duty highway patrol officer who was driving and three members of his family.
That crash played a major role in renewing government scrutiny of unintended acceleration complaints leading to Toyota's huge recall.
"While all of the facts surrounding the latest incident have yet to be fully known and investigated ... it certainly does have great potential to erode whatever consumer confidence was rebuilding for Toyota," said Geoff Sundstrom, a spokesman for the American Automobile Association.
Unintended acceleration in the company's Toyota and Lexus vehicles has been linked to at least five US crash deaths since 2007. Authorities are investigating 47 other Toyota crash deaths over the past decade.
Reuters