The US National Highway Traffic Safety Administration (NHTSA) has opened a ‘preliminary evaluation’ into an estimated 30,000 2007 and 2008 model year Toyota Camry Hybrid sedans after receiving 59 complaints alleging intermittent loss of assisted braking, resulting in increased stopping distances.

This is the first step in a process that can lead to a recall should regulators determine that a manufacturer needs to address a safety problem.

Two accidents, but no injuries, were listed in NHTSA documents cited by the Reuters news agency. The complaints reportedly show an increasing trend with more than half received in the past eight months, according to the documents.

Each complaint alleges multiple incidents of either delayed braking activation or increased brake pedal effort, Reuters said. About 40% of the incidents occurred at speeds of 40 miles per hour or more, according to NHTSA.