Federal auto safety regulators are investigating complaints of power loss in 2016 to 2019 Chevrolet Volts.

The National Highway Traffic Safety Administration said it’s gotten 61 consumer complaints about power loss at various speeds and that the car may not restart after such an episode.

The incidents involved either complete power loss or reduced power in the hybrid vehicles, the agency said in a preliminary investigation report.

Some consumers said they got little to no warning that the power loss was about to happen, the report said.

The agency said Volt maker General Motors previously issued a technical service bulletin about the possibility of Volts failing to start, indicating the problem involves the battery energy control module, or BECM, which should be replaced, though GM didn’t recall effected vehicles.

Regulators discussed the issue with the company several times, said the agency, which now intends to fully determine the scope of the problem.

GM stopped making the Volt in early 2019.

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