In addition to tough questioning by the US Congress, Toyota is also facing a federal criminal investigation and a Securities and Exchange Commission probe (SEC) into what the automaker told investors.

Toyota, says a federal grand jury in New York is investigating into the problems relating to unintended acceleration of Toyota vehicles and the braking system of the Prius.

Meanwhile, the SEC, is trying to find out whether the company has done something wrong in its information disclosure. The investigations raise the possibility of hefty fines for the automaker, or possible indictment. And they create new challenges for Toyota officials scheduled to testify at Congressional hearings on Tuesday and Wednesday, about whether the company took safety problems seriously.

Federal prosecutors will investigate whether individuals broke any laws, and potentially charge them instead of mounting a case against the entire corporation.