Though Toyota has been hit by another wave of recalls, or potential recalls, there was good news of sorts from the US - regulators there have yet to find any electronic defects in their vehicles, a local vehicle safety official reiterated Wednesday, as a scientific panel began studying potential causes of unintended acceleration.

Dow Jones noted that some members of Congress, consumer advocates and product liability lawyers have suggested that engine electronics may have played a role in problems that led Toyota to recall more than 8m vehicles globally for sudden-acceleration and accelerator pedal problems. Those critics have questioned the adequacy of efforts by Toyota and government regulators to study electronics.

"We have not actually been able to find a defect of electronic throttle control systems" in Toyota cars, Dan Smith of the National Highway Traffic Safety Administration told a panel of the National Academy of Sciences.

He said regulators have only been able to identify two causes of the Toyota problems -floormat entrapment of the accelerator pedals and pedals that are slow to return to idle.

The academy is undertaking a broad study of unintended acceleration and will eventually offer recommendations on how regulators should improve their ability to set standards and identify defects.

Smith said his agency hasn't ruled out the possibility of electronic defects and that investigations are ongoing. NHTSA is working with NASA engineers to study the Toyota recalls, including possible electronics defects.

NHTSA chief David Strickland told the academy panel that unintended acceleration is a problem that affects all major car manufacturers.

"Complaints of unintended acceleration are not - repeat, not - exclusive to Toyota," Strickland said.