A routine crash test for the Chevrolet Volt has prompted a federal investigation of the lithium-ion batteries that power electric cars.

According to Reuters, the incident has led to the National Highway Traffic Safety Administration turning its attention toward manufacturers of electric vehicles, and asking for details about how they handle the batteries and minimize fire risk.

However, the agency has made it abundantly clear that the incident appears to be a fluke thus far, and reiterated its support of the Volt and other electric vehicles.

Various reports indicate that the Volt crash test occurred in May, and the fire broke out several weeks later in the massive, T-shaped battery that runs from the back of the car and through the center of its frame. General Motors stated that it was not aware of any prior incidents like this with the Volt, and the NHTSA said it hasn’t received any consumer complaints about this type of fire with the Volt or other electric vehicles.

General Motors and NHTSA were also unable to replicate the fire in follow-up tests, so it seems like electric vehicles continue to get the green light from federal safety agencies.

“First and foremost, I want to make this very clear: The Volt is a safe car,” said GM’s chief engineer for electric vehicles, Jim Federico, in an official statement. “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.”