U.S. launches probe of Prius

The U.S. National Highway Traffic Safety Administration said it has received 124 complaints about momentary braking problems after motorists rolled over bumps or potholes with the third-generation Prius.

Drivers reported four crashes related to the braking problems, NHTSA said. The investigation covers the 2010 model year Prius.

"We have heard about NHTSA's intention to begin investigation. Toyota will fully cooperate," Toyota spokeswoman Cindy Knight said.

Toyota changed the software controlling braking in the Prius on models manufactured in Japan from last month, a step it had not announced before Thursday.

It was not clear whether -- or how quickly -- the automaker would move to apply the fix to other Prius models already sold to American consumers.

Toyota shares dropped another 3 percent in New York on Thursday. The stock has lost 20 percent since it announced a sweeping recall for accelerator problems in late January.

The new probe of the Prius threatens to compound a consumer safety crisis that has hit Toyota's sales, financial results and reputation for quality and prompted the recall of more than 8 million vehicles around the world for problems with uncontrolled acceleration.

The 2010 model Prius is a completely redesigned version of the iconic hybrid that Toyota has said is the most important vehicle in its line-up and almost a brand on its own.

Analysts and rivals say the Prius has emerged as a kind of environmental "halo car" for Toyota, an icon of green design with an intense following among loyalists that has lifted the public image of the whole company.