US investigators doubt Toyota fully understands its accelerator problems and are even less sure that new floor mats are an adequate solution.
A congressional committee will publicly grill the Japanese automaker's top brass as well as federal regulators later in February over the safety crisis that has led to 8.7-million vehicle recalls worldwide.
Investigators briefed lawmakers in a memorandum critical of both Toyota and the US government's National Highway Traffic Safety Administration, which said:
"There appears to be a growing body of evidence that neither Toyota nor NHTSA have identified all the causes of sudden unintended acceleration in Toyota vehicles.
"Moreover, there is substantial evidence that remedies such as redesigned floor mats have failed to solve the problem.
"This hearing will examine the question of whether Toyota and NHTSA have failed to meet their statutory and regulatory responsibilities."
Committee chairman Henry Waxman said he had sent letters to five insurers requesting information they had received from customers about Toyota problems. He said the committee was also seeking details of any warnings the companies may have passed on to the NHTSA, after reports said insurers had informed the agency about a pattern of customer complaints.
Toyota meanwhile announced it was recalling hundreds of thousands of hybrid vehicles worldwide, including its best-selling Prius, due to a flaw in the braking system, plunging it deeper into crisis.
Facing a barrage of complaints ranging from unintended acceleration to brake failure, Toyota is scrambling to reassure drivers it did not sacrifice safety in its successful drive to become the world's largest automaker.
Class action lawsuits have piled up in the US amid accusations Toyota knew about the problems for years as the company follows up its recalls with desperate attempts to redesign floor mats and sticking accelerator pedals. - AFP