WASHINGTON (AP) -- A House committee on Friday questioned how rigorously Toyota has tested its vehicles for sudden acceleration, and asked the Japanese automaker for more records on the safety issues.

The House Energy and Commerce Committee told Toyota executive Jim Lentz in a letter that there is "an absence of documents" to show whether the company thoroughly investigated the possibility of unintended acceleration. The committee demanded to know who is involved with the testing and receive quarterly reports detailing allegations of the unwanted acceleration.

"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," wrote Chairman Henry Waxman, D-Calif., and Rep. Bart Stupak, D-Mich.

Toyota has recalled more than 8 million vehicles worldwide to address gas pedals that can become sticky or trapped under floor mats, prompting scrutiny from Congress. The world's No. 1 automaker has said it is investigating reports of sudden acceleration but remains confident there are no problems with Toyota's electronic throttle control systems.

Adding to the doubts, the government has received more than 60 complaints from Toyota owners who had their vehicles fixed following the recalls but say they've had more problems with their vehicles surging forward unintentionally. Toyota dealers have been fixing the accelerator pedals but the National Highway Traffic Safety Administration said Thursday that if the remedy provided by Toyota is not addressing the issue, the government could order the company to provide a different solution.

Toyota did not immediately respond to the committee's letter on Friday.

Toyota hired a consulting firm to study whether electronic problems could cause unintended acceleration. The firm, Exponent Inc., released an interim report that has found no link between the two. But committee investigators have said the Exponent test was flawed because it studied only a small number of Toyota vehicles.

In the letter, Waxman and Stupak also request more details on brake override systems and "black box" information in Toyota vehicles.

Toyota plans to install brakes that can override the gas pedal in future models and many vehicles already on the road. The safety measure is meant to prevent the unintended acceleration that has caused some Toyota drivers to speed out of control.

The committee also wants to know what information is available in Toyota electronic data recorders. The "black box" information could help investigators learn more about what is happening in the vehicles before crashes. A review by the Associated Press found that Toyota has been inconsistent -- and sometimes even contradictory -- in revealing what the devices record and don't record, such as critical data about whether brake or accelerator pedals were depressed at the time of a crash.

NHTSA has linked 52 deaths to crashes allegedly caused by Toyota's acceleration problems.