DETROIT » U.S. safety regulators are investigating problems with the power brakes in the Mazda CX-9 crossover SUV.

The National Highway Traffic Safety Administration says it has seven complaints of unexpected loss of power-assisted brakes. No crashes have been reported.

The probe covers about 62,000 of the SUVs from the 2010 and 2011 model years.

The agency says people have complained about increased brake pedal effort and reduced brake effectiveness. Some have heard a hissing noise when they step on the brakes.

Investigators will check into whether the problem is big enough to cause a recall.

Mazda says it is cooperating with NHTSA in the investigation. Any owner with concerns about their vehicle should call their dealer to schedule an inspection, spokesman Jeremy Barnes said in an email.