NEW YORK (CNNMoney.com) -- The National Highway Traffic Safety Administration announced Thursday it is opening a formal investigation into problems with the braking system of Toyota's Prius hybrid.
Toyota has yet to announce a recall of the Prius, it's fourth-best selling vehicle model in the United States and the best-selling model in Japan. But it has admitted to a software glitch that is causing problems with its braking. It said it is looking further at the best way to repair the problem.
The Prius, which is built in Japan, is not one of the eight models that was affected by two recalls recently to fix problems with sticking gas pedals. All of those models were built at North American plants.
NHTSA said its Office of Defects Investigation has received 124 reports from consumers about problems with the Prius brakes, including four reports alleging that involved crashes. Investigators have spoken with consumers and conducted preliminary field work.