WASHINGTON – Separate House committees are demanding more information from Toyota and government regulators after executives from the embattled Japanese automaker appear to have given conflicting answers about the causes of runaway vehicle acceleration plaguing the company.

The House Energy and Commerce Committee sent a letter to Toyota U.S. sales head Jim Lentz on Friday asking for deep and complete documentation showing why Toyota is confident that the runaway acceleration is caused by mechanical, not electronic, problems as the company has maintained.

Also on Friday, the House Oversight and Government Reform Committee wrote to the National Highway Traffic Safety Administration asking what it is doing to find the cause of the problem, following reports that Toyota owners continue to experience runaway acceleration – even after they have taken their vehicles to Toyota dealers to make company-ordered fixes.

Last month, Lentz appeared before the Commerce committee and was asked if he thought the current Toyota recalls – 8 million vehicles have been recalled to fix floor mats and sticking gas pedals – would solve the acceleration issue. “Not totally,” Lentz said.

The next day, Toyota released a statement and Toyota President Akio Toyoda testified before another congressional committee, saying that there’s nothing wrong with Toyota’s electronics and that the recall fixes will work.

“We do not understand the basis for Toyota’s repeated assertions that it is ‘confident’ there are no electronic defects contributing to incidents of sudden unintended acceleration,” reads the commerce committee’s letter, from Chairman Henry Waxman, D-Calif., and Rep. Bart Stupak, D-Mich.

The letter demands interviews next week from Toyota officials who personally tested the electronics that some critics believe to be at the heart of the runaway acceleration.

The tone of the letter suggests that Toyota is trying the patience of Congress.

“After we sent our letter on February 22, Toyota provided a few additional documents to the committee early in the morning on the day of the hearing,” reads the letter. “Several of these documents were written in Japanese.”

Transportation Secretary Ray LaHood has said there is a “broken” business model between Toyota headquarters in Japan and Toyota North America, and that Japan has not listened to what North America has been saying.

The oversight committee, which sent a letter to NHTSA Administrator David Strickland, is responding to recent reports of continued runaway acceleration in Toyotas that dealers have fixed.

The letter asks the traffic safety agency to create a detailed database of vehicles that continue to experience runaway acceleration and to deliver periodic updates to Congress on the agency’s investigation of the problem.

On Friday, the NHTSA said that it has received 60 complaints from Toyota owners in this category. The agency said it will interview each of the 60 drivers to investigate the situation.

“We are determined to get to the bottom of this,” Strickland said in a statement.