The United Auto Workers expanded its strike against General Motors Co. to include plants in Spring Hill, Tennessee, as talks on a new contract fail to reach a deal.

Spring Hill has 3,200 workers at an assembly plant along with engine and metal-stamping operations. The assembly plant, which once made Saturn cars, assembles mid-size SUVs and the Cadillac Lyriq electric vehicle. A weekend crew of more than 70 workers walked out at 5 p.m. local time on Saturday, according to Jason Spain, shop committee chairman of Local 1853. The new strike was confirmed by UAW spokesman Jonah Furman.

More than six weeks after the UAW began its historic strikes against Detroit’s legacy automakers, GM is the only one of the three companies that hasn’t reached a tentative agreement with the union. Negotiations at GM have been held up by disagreements over issues including temp workers, according to people familiar with the talks who weren’t authorized to speak publicly.

Stellantis NV reached a deal with the UAW on Saturday, three days after Ford Motor Co. Both agreements will need to be voted on by the companies’ union members.

Like Stellantis and Ford, GM has agreed to a 25% wage increase for hourly workers along with cost-of-living allowances, according to people familiar with the discussions.

(Updated with strike details in second paragraph.)