FLINT, Mich. (CNN) -- As an arbitrator continued hearings Friday on whether two United Auto Workers union strikes against General Motors Corp. are permissible, the automaker announced two plants will resume operations.
In the meantime, the strikes may be spreading. UAW Vice President Richard Shoemaker said laid-off workers at a GM truck plant in Janesville, Wis., may join the strikes. Shoemaker said the Wisconsin workers had asked the international union to give GM the required five-day notice that they will walk out. All 4,000 workers at the truck plant have been laid off because of the strikes in Flint.
Shoemaker also said he did not believe workers at GM's Saturn plant in Spring Hill, Tenn., would wait a full 30 days before taking action on a strike authorization they approved last week.
Gerry Holmes, a GM spokesman, said the company had found parts suppliers, allowing GM to restart operations at its Corvette plant in Bowling Green, Ky., next week. He added that a plant in Silao, Mexico, that produces sport/utility vehicles also will reopen Monday.
Holmes said GM had found "alternative sources of parts" but would not confirm reports that the parts come from companies in England and Japan.
Holmes also confirmed operations have restarted at a Delphi plant in Renoso, Mexico, that produces instrument panels.
In the arbitration hearings, GM contends that the union is attempting to strike over national issues that are "non-strikeable" under the UAW-GM national agreement. Those issues include product placement and investment.
The UAW says issues at the Flint Metals Center and the Delphi East plant include concerns over health and safety, which are strikeable issues.
If Thomas Roberts, the arbitrator, decides for GM, the company could seek an injunction forcing 9,200 workers back to their jobs.
GM also could sue the union for its losses, which now total more than $1 billion.
However, Shoemaker has said that if the workers in Flint are forced back to work, UAW workers at other plants will strike. Workers in Ohio and Indiana already have voted to strike, as have workers in Wisconsin and Tennessee.
Shoemaker said little progress was being made in negotiations, despite a report in the Wall Street Journal stating there was a new flurry of talks between upper levels of the union and GM.
The strikes, which began June 5, have idled more than 200,000 GM workers and virtually halted the automaker's North American assembly operations.
GM has said that many of its plants are inefficient and the company needs more flexibility to compete against other automakers. The UAW has charged GM has failed to live up to promises to improve its North American assembly plants and is farming out jobs to overseas plants where labor costs are lower.
GM (GM) shares rose 1-7/16 to 71-7/8 in midday trading.