NEW YORK (CNNMoney.com) -- Federal investigators are looking into whether the problem with Toyota gas pedals goes beyond the fix announced by the company Monday and involves the vehicles' electrical system.
The National Highway Transportation Safety Administration also is looking into possible civil penalties for Toyota (TM).
Both the investigation into the vehicles' electrical system and the possible penalties were confirmed by an agency official who asked to remain anonymous. The official says the safety agency is looking at the possibility that electromagnetic interference might somehow be causing Toyota's electronic throttle control systems to malfunction, though NHTSA has not seen evidence to support that yet.
Another NHTSA official said this is not an official defect investigation.
"We will continue to cooperate fully with NHTSA on all vehicle safety issues," said Brian R. Lyons, safety and quality communications manager for Toyota Motor Sales, U.S.A.
Toyota has said recently that it has rigorously tested its electronic throttle control systems under a variety of circumstances, including subjecting them to various forms of electromagnetic radiation while in use, and that it has been unable to find any problems.
Toyota recalled 2.3 million vehicles on Jan 21 due to problems with sticking gas pedals that cause the vehicles to accelerate out of control and later halted the sale of the eight vehicles involved in the recall.
Monday, company officials announced they had found a solution that involved reinforcing the pedal assembly with a part that is being rushed to dealerships.
The company restarted sales of the vehicles that have been fixed in that manner.
Transportation Secretary Ray LaHood issued a statement Tuesday saying that "Toyota is taking responsible action" in the fix, but criticizing its process.
"It unfortunately took an enormous effort to get to this point," he said, saying DOT officials had to fly to Japan to push the company to fix the pedal.
"We're not finished with Toyota and are continuing to review possible defects and monitor the implementation of the recalls," he said in the statement.
Toyota issued a response to LaHood in which it said: "We are very grateful for the advice of all the government agencies involved and feel that through our handling of the recall we have a chance to regain the trust of our customers."
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