The US Transportation Department has opened an investigation into brake problems in the 2010 Toyota Prius.

The move follows an admission from Toyota that it had had a problem with the brake system in the hybrid, which the carmaker said was fixed in January.

The National Highway Traffic Safety Administration has received 124 reports from drivers about the issue, including four of crashes.

There have been no reports of any such accidents in the UK.

The investigation will look into allegations of momentary loss of braking capability while travelling over uneven road surfaces, potholes or bumps. However it will not suspend sales.