The exact dates of the closures were not known, but both people said they will occur around the normal two-week shutdown in July to change from one model year to the next. Neither person wanted to be identified because workers have not been told of the shutdowns.
GM spokesman Chris Lee would not comment other than to say the company notifies employees before making any production cuts public.
The automaker is living on $13.4 billion in government loans and faces a June 1 deadline to cut its debt, reduce labor costs and take other restructuring steps. If it doesn't meet the deadline, the company's CEO has said it will enter Chapter 11 bankruptcy protection.
United Auto Workers officials at several factories said they have meetings scheduled Thursday and Friday with plant managers and GM human resource officials to discuss production changes.
The automaker's sales were down 49 percent in the first quarter compared with the same period last year, and GM had a 123-day supply of cars and trucks at the end of March, according to Ward's AutoInfoBank. GM already has more than a six-month supply of several models.
On Monday, GM announced about 1,600 white-collar workers wouldas the troubled automaker accelerates cost cuts in order to qualify for more government aid.
GM North America President Troy Clarke said Monday in an e-mail to employees that the layoffs are needed to ensure the company's long-term viability.
"In these unprecedented times, GM is reinventing every aspect of our business, including our organizational size and structure, to create a lean and agile company," Clarke wrote in the e-mail obtained by The Associated Press.