The Transportation Department announced Thursday it plans to investigate possibly widespread brake problems with the Toyota Prius.

The decision arrives as lawmakers and White House officials are separately considering a slew penalties for the Japanese automaker, which halted the sale of eight different car models this month because of a software problem plaguing other cars' accelerator pedals.

The National Highway Traffic Safety Administration (NHTSA), which will lead the investigation, revealed Thursday it has so far received 124 consumer complaints about faulty Toyota Prius models, including four complaints that involved car crashes.

The agency added it had already started gathering information about those incidents; meanwhile, Secretary Ray LaHood said Thursday he had been in close touch with Toyota's president, Akio Toyoda, about the situation.  

“Safety is our top priority,” said LaHood, who had previously not spoken directly with Toyota's president. “That is why in recent weeks NHTSA has also issued a consumer advisory on the recall of several models of Toyota vehicles and the Pontiac Vibe involving pedal entrapment and sticky accelerator pedals. We will continue to monitor these issues closely.”

LaHood and other federal officials have implored Toyota owners this week to "exercise concern immediately," in connection with an accelerator problem that forced the manufacturer to recall about 6 million of its cars.

The mass alert has ultimately infuriated lawmakers, some of whom are now calling for hearings, investigations and penalties on Toyota for failing to catch the problem sooner.

Toyota officials have opened their own investigation too, at the request of the Japanese government. Officials at the firm maintain the brake problem, in particular, could be fixed with a simple software tweak.