General Motors resumed production late on Thursday at a large car assembly plant in Detroit after production halted a week ago due to a quality problem with new Northstar V8 engines used in Cadillacs, according to Reuters .

GM has lost daily output of about 970 Cadillac DeVilles, Sevilles and Buick LeSabres, some of its most profitable cars, Reuters said, citing company spokesman Dan Flores.

GM would not detail the quality problem but claimed no affected cars had been shipped to dealers and that lost production would be made up later, Reuters added.