A U.S. auto safety regulator said Friday it is opening an investigation into 73,000 Chevrolet Volt plug-in hybrid cars over reports of loss of power, failures to restart and other issues.

The National Highway Traffic Safety Administration said it was opening the preliminary evaluation into the 2016 through 2019 model year Chevrolet Volt after 61 complaints tied to the Battery Energy Control Module (BECM). Some complaints reported there was little to no warning before the loss of operating power or reduced power mode occurred.

General Motors previously issued a technical service bulletin saying if vehicles fail to restart, the BECM may need to be replaced and reprogrammed but has not recalled vehicles, NHTSA said. GM ended production of the Volt in early 2019.