FLINT, MI - SEPTEMBER 16: United Auto Workers (UAW) members picket at a gate at the General Motors Flint Assembly Plant after the UAW declared a national strike against GM at midnight on September 16, 2019 in Flint, Michigan. Nearly 50,000 members of the United Auto Workers went on strike after their contract expired and the two parties could not come to an agreement. (Photo by Bill Pugliano/Getty Images)
Bill Pugliano/Getty Images North America/Getty Images
FLINT, MI - SEPTEMBER 16: United Auto Workers (UAW) members picket at a gate at the General Motors Flint Assembly Plant after the UAW declared a national strike against GM at midnight on September 16, 2019 in Flint, Michigan. Nearly 50,000 members of the United Auto Workers went on strike after their contract expired and the two parties could not come to an agreement. (Photo by Bill Pugliano/Getty Images)
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(CNN Business) —  

The United Auto Workers union went out on strike against General Motors Sunday night, the first work stoppage in the US auto industry in 12 years.

The union’s nearly 50,000 hourly fulltime and temporary workers walked out at 31 GM factories and 21 other facilities, spread across nine states, mostly in the center of the country. It’s the largest strike by any union against any business since the last strike at GM in 2007.

The strike started at 11:59 pm Sunday night. The two sides did not formally meet Sunday after the union declared its intention to strike at a morning press conference, although union spokesman Brian Rothenberg said that the dialogue between the two sides was ongoing. A new meeting of the two sides is set for 10 a.m. Monday.

The union said that GM was putting profits ahead of employees who helped to turn the company around when it went through bankruptcy and federal bailout a decade ago.

The union is seeking higher hourly wages, lump sum payments and a better profit sharing plan. It also wants GM to agree to limit the use of temporary workers and give them a clearer path to permanent employment. In addition, the UAW says the two sides are far apart on other issues including health care benefits and job security.

General Motors said it made a substantial offer, including higher pay and profit sharing, along with investment to bring new jobs. It said it offered to commit to invest $7 billion in coming years to preserve 5,400 jobs. It also promised a “solution” for two of the four plants currently slated for closure: one in Detroit and another in Lordstown, Ohio.