The cause of the fire, which happened three weeks after the vehicle was crash-tested in the agency’s New Car Assessment Program, is still being investigated but the NHTSA said it believed the battery had been damaged in the impact. Despite damage to other vehicles nearby, nobody was injured.

In its statement, the agency said this was the only example of a battery-related post-accident fire on any vehicle with a lithium ion battery, despite its own extensive testing and similar tests done by General Motors. Both electric and conventionally powered vehicles are a potential fire hazard after a crash, it added.

Working with electric vehicle manufacturers, the National Fire Protection Association and the United States Department of Energy, the NHTSA is now developing a series of protocols for dealing with accident-damaged electric vehicles. These will be passed on to emergency services to avoid injuries and work out how to discharge and store damaged batteries.

‘The Department of Energy and the National Fire Protection Association already collaborate to ensure first responders know the risks and the appropriate steps to take so they can perform their jobs safely given the shock hazard that a damaged electric vehicle may present, and NHTSA will work closely with these organisations to ensure that guidance for the emergency response community reflects the information NHTSA obtains,’ the NHTSA statement said.

 Jim Federico, GM chief engineer for electric vehicles, commented: ‘First and foremost, I want to make this very clear: the Volt is a safe car. We are working cooperatively with NHTSA as it completes its investigation. However, NHTSA has stated that based on available data, there’s no greater risk of fire with a Volt than a traditional gas-powered car.

‘Safety protocols for electric vehicles are clearly an industry concern. At GM, we have safety protocols to depower the battery of an electric vehicle after a significant crash. We are working with other vehicle manufacturers, first responders, tow truck operators, and salvage associations with the goal of implementing industry-wide protocols.’