The NHTSA has warned owners of some 2017-2019 Chevrolet Bolt vehicles in the US to park their cars outside and away from homes until their vehicles have been repaired, due to a new recall for the risk of fire.

GM has issued a recall of 50,932 vehicles for the potential of an unattended fire in the high voltage battery pack underneath the back seat's bottom cushion. The affected vehicles' cell packs have the potential to smoke and ignite internally which could spread to the rest of the vehicle and cause a structure fire if parked inside a garage or near a house.

These vehicles can catch fire even if they are turned off, parked, and disconnected from a charging unit. NHTSA has confirmed five known fires with two injuries; at least one of the fires spread from the vehicle and ignited a home. Until these recalled vehicles have been repaired, the safest place to park them is outside and away from homes.

The Office of Defects Investigation (ODI) of the National Highway Traffic Safety Administration (NHTSA) has received two Vehicle Owner Questionnaires (VOQs) regarding a model year (MY) 2018 and a MY 2019 Chevrolet Bolt EV and alleging that the vehicles caught fire under the rear seat while parked and unattended. ODI conducted additional research, and found a MY 2017 Bolt EV with a similar burn pattern in the interior rear seat area.

In the three cases identified, fire damage appeared to be concentrated in the EV battery compartment area with penetration into the passenger compartment from under the rear seat. The root cause of these fires is unknown. One of these incidents reported smoke inhalation injuries.

The Detroit News reported General Motors was voluntarily recalling 68,667 Bolt EVs manufactured between 2017-2019 as it worked with NHTSA to pinpoint what caused multiple battery fires.

The automaker had found five confirmed incidents of battery fires on the Bolt when the batteries were either at full charge or almost fully charged. Three of those five incidents were highlighted in October by NHTSA, which is investigating the fires. GM has found two reports of smoke inhalation injuries out of the five.

The report said GM was still unsure what caused the fires but has found similarities in the five incidents, including the amount of battery charge and that the cells used in these batteries were all manufactured at a Korean LG Chem plant. The 2020 Bolts are not included in the recall because their cells are manufactured with a different chemistry.

"The safety of our products is the highest priority for the entire GM team," Jesse Ortega, executive chief engineer for the Chevrolet Bolt EV, told the Detroit News during a briefing with media. "We will continue to cooperate with NHTSA and we are working around the clock on our own investigation to identify the issue."

The recall, which covers the 50,900 Bolts in the US, will require dealerships to reflash the vehicles' battery software to limit the maximum state of charge to 90%, Ortega said: "We believe this action will reduce the risk of battery fire while we work to identify the issue, and determine the appropriate final repair. We expect this software update to be available beginning 17 November."

GM, which became aware of the incidents at the start of this summer, doesn't believe the issue is present in all of the vehicles it's recalling, but GM believes "it is prudent to limit the state of charge as a precaution as we continue our investigation," Ortega said. 

Until consumers get their charging limits adjusted at the dealership, Chevrolet is asking them to change their settings to use 'hilltop reserve' for 2017 and 2018 Bolts, the Detroit News said. Consumers with 2019 Bolt EVs should use the target charge level option and set the maximum capacity to 90%.

More than 77,800 Bolts from 2017-20 model years are covered in the NHTSA probe into why fires were ignited in the electric battery compartment area, the report added.