US federal safety regulators have opened a new investigation into 724,000 Ford Escape, Fusion and Mercury models over reports of sudden loss of most engine power, Detroit News reported Monday.

The National Highway Traffic Safety Administration said it had opened a preliminary investigation into the 2009-2011 Escape, Fusion, Mercury Mariner and Milan.

Ford made a design change in 2009 to address the complaints but did not recall the vehicles.

Depending on condition of throttle control system malfunction of the affected vehicles, a driver may experience varying levels of reduced engine performance. Vehicles are not likely to unexpectedly stall as a result of this condition, but drivers may characterize the reduced functionality as a stall, even though their vehicle may still has some capability.

NHTSA's Office of Defects Investigation received 59 complaints alleging incidents of engine stall while driving in model year 2010-11 Ford Fusion vehicles. Approximately 60 percent of the incidents occurred at speeds of 40 miles (64 kilometers) per hour or more.

NHTSA opened the formal investigation after receiving a petition in August from the North Carolina Consumers Council seeking a broad investigation into electronic throttle body failures resulting in engine stall or surge in 2005-12 Ford Escape SUVs.