General Motors will buy back Chevrolet Volts from owners who are concerned their plug-in hybrid cars could catch on fire.

GM CEO Dan Akerson confirmed the buy-back offer just days after the National Highway Traffic Safety Administration (NHTSA) in the US launched a formal investigation into the Volt. Three Volts caught fire this year after being crash tested by NHTSA. The fires – caused by damage to the vehicles’ lithium-ion battery packs – started between one and three weeks after the crash tests were conducted.

Akerson told the Associated Press his company was offering to buy back every one of the 6000-plus Volts on the road in the US because he was determined to keep customers happy. If NHTSA rules that a recall is necessary, he said GM would cooperate fully and repair every Volt it has produced.

"If we find that is the solution, we will retrofit every one of them. We'll make it right," Akerson said.

NHTSA initially crash tested the Volt in May. It earned a five-star safety rating, although three weeks after the test the vehicle caught fire. The government tester sought to recreate the results in three additional crash tests last month. One car sparked and smoked and another caught fire - both occurring days after the crash tests - prompting NHTSA to initiate a formal safety defect investigation.

Akerson told AP the NHTSA tests were more invasive than conventional tests, intruding into the Volt's South Korea-sourced battery pack by approximately 10-12cm, at least double the standard 5cm. GM says no Volts that have been crashed by owners have caught fire.

Chevrolet is alerted to real-world crashes by the Volt's On Star communications and safety system, and engineers are sent to drain the battery within 48 hours - a precaution that has so far proved effective.

On top of the buy-back scheme, GM has offered Volt customers the option to swap their vehicle for a loan car until the investigation reaches a conclusion, although the manufacturer says few have taken up the offer. As of the end of last week, only two Volt owners had requested a loan car.

The Holden Volt (a rebadged and localised version of the Chevy) will go on sale in Australia towards the end of next year.