LOS ANGELES – General Motors Co. is offering to provide a free loaner car to Chevrolet Volt owners who are concerned about the safety of their vehicles after a series of fires that occurred during crash-testing of the electric vehicle and its batteries.

“Our customers’ peace of mind is the most important thing. This technology should inspire confidence and pride, not raise any concern or doubt,” said Mark Reuss, president of GM North America.

Reuss said GM will contact all Volt owners “to reassure them” that the vehicles are safe to drive and won’t spontaneously catch fire, even in a crash.

GM has sold about 6,000 of the vehicles, which can travel about 40 miles just on battery power before a gas engine kicks in and functions as a generator to extend the range an additional 300 miles.

Federal officials on Friday launched a formal safety-defect investigation into GM’s plug-in hybrid vehicle after crash tests on several Volts and their batteries resulted in fires. In one case, a fire that started in one of the test vehicles consumed three others parked nearby.

The National Highway Traffic Safety Administration said it was “concerned” that damage to the Volt’s batteries sustained in tests designed to replicate real-world crash scenarios resulted in the vehicles catching fire.

The problem occurs when electricity is left stored in the batteries for some time after a crash, said Mary Barra, GM’s senior vice president of global product development.