House investigators say there's growing evidence that not all the causes of Toyota's acceleration problems have been identified.
A Democratic staff memo from the House Oversight and Government Reform Committee says neither Toyota nor federal safety officials have identified all causes of unintended acceleration.
The memo says there's substantial evidence that remedies such as redesigned floor mats have failed to solve the problem.
The document was prepared for a hearing originally was scheduled for Wednesday, but has been postponed until Feb. 24 because of an expected snowstorm.
The hearing will examine whether Toyota and the National Highway Transportation Administration have failed to meet their responsibilities to ensure the safety of the vehicles.
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