UPDATE: Toyota Executive Tells Congress Recalls Might Not Be Enough

The head of Toyota's American sales operation told a House committee on Tuesday that the automaker's massive recall might not solve the problem of sudden acceleration in its vehicles.

James Lentz testified that there's no hard evidence that a faulty electronics system was to blame for the acceleration issue. But, he added, Toyota continues "to look for potential causes," The New York Times reported.

"We need to be vigilant and continue to investigate" all consumer complaints, Lentz told the House Energy and Commerce Committee. He said there is the possibility "of mechanical, human or some other type of error."

Committee Chairman Henry Waxman (D-Calif.), a persistent and well-informed advocate of consumer causes, criticized Toyota's slow response to the recall, which numbers more than 8 million vehicles worldwide. "The possibility of electronic defects must be actively investigated," Waxman told Lentz.

Toyota claims that floor mats and sticky gas pedals might be the cause of sudden acceleration, an assertion supported in testimony by Transportation Secretary Ray LaHood. He said his department had found no evidence of computer problems.

Waxman cautioned Toyota that his panel is looking as far back as 2004 for signs that regulators overlooked evidence of engine defects in Toyotas.

Documents obtained by the committee "appear to show that Toyota consistently dismissed the possibility that electronic failure could be responsible for incidents of sudden unintended acceleration," they wrote.

Waxman's committee has wide jurisdiction and an aggressive staff of investigators.

On Wednesday, Akio Toyoda, president of Toyota, is scheduled to testify before the House Oversight and Government Reform Committee. He is expected to tell lawmakers the Toyota compromised quality by growing too quickly in the U.S., but will take steps to improve quality control, according to The Associated Press.