DETROIT (AP) — Workers at five General Motors Corp. factories are either on strike or threatening a strike as disputes over local contracts continue to surface.

The latest strike warning came from a United Auto Workers local at a metal parts stamping factory in Mansfield, Ohio, that employs about 1,400 hourly workers.

GM spokesman Dan Flores said Tuesday it's unclear when the five-day strike warning is effective. A message was left for the Mansfield union president.

The Mansfield plant is the fifth GM local union to threaten a walkout or go on strike over local contract issues.

A local at a plant in Delta Township near Lansing went on strike Thursday, while locals at a Warren transmission factory, a Grand Rapids metal fabricating plant and a factory in Kansas City, Kan., that makes the strong-selling Chevrolet Malibu all have threatened walkouts.

Flores says negotiations are under way at all the plants in hopes of resolving the issues without further strikes.

At the Fairfax Assembly Plant in Kansas City, a five-day strike notice was extended until Thursday afternoon. A message was left for Jeff Manning, president of the local union at the plant that makes the Chevrolet Malibu.

In addition, a local representing about 1,500 workers at GM metal stamping and powertrain operations in Parma, Ohio, near Cleveland have rejected a tentative local contract with the company.

Local 1005 President Tito Boneta said Tuesday that local leaders will talk to members to find out what problems they had with the deal. He said they may call for another vote, and that a strike is unlikely.

"We're going to find out from the membership what was their issues," Boneta said. "Was it a misunderstanding or not and understanding of the language?"

Local plants negotiate their own operating agreements separate from the national contract, which was settled last year. The local contract deals with issues such as overtime and work rules.

Industry analysts have speculated that the strike and threats are an effort by the UAW to get GM to put pressure on American Axle and Manufacturing Holdings Inc. to settle a lengthy strike.

GM accounts for 80 percent of American Axle's parts business. About 3,600 UAW workers at five American Axle plants have been on strike since Feb. 26. Negotiations are continuing.

UAW President Ron Gettelfinger says the threats are about local contract issues and have nothing to do with American Axle.

GM shares closed Tuesday down 76 cents, or 3.6 percent, at $20.51.