NHTSA is investigating fuel leak complaints in 614,000 Chevrolets. No vehicles have been recalled.
The investigation, disclosed on Sunday, involves 2008-10 Chevrolet Cobalts and 2008-09 HHRs. There are 208 owner complaints with 39 specifically noting "puddles or drips" from leaks. No injuries, accidents or fires have occurred because of the leaks.
General Motors said in a statement to Reuters that it will continue to cooperate with NHTSA in the investigation.
The leaks come from corroding metal fuel lines beneath the vehicle. The corrosion occurs in polymer blocks connecting fuel lines to the underbody, beneath an insulation wrap heat shield. The blocks are near the exhaust pipe and muffler.
The Associated Press reported the investigation on Tuesday.