Hundreds of GM workers in Oshawa were told to stay home Wednesday after a strike by auto workers in the U.S. limited the number of parts shipped to Canada, shutting down the truck assembly line at the plant.

Approximately 49,000 United Auto Workers in the U.S. went on strike against General Motors on Sunday night.

On Tuesday afternoon, 1,200 workers in Oshawa were told to go home. Another 650 workers on the morning shift were told they weren't needed on Wednesday.

A spokesperson for GM said approximately half of the production at the Oshawa plant was being affected by the UAW strike.

"Some vehicles have been disrupted because of a lack of parts," David Paterson, GM's vice-president for corporate and environmental affairs, confirmed, explaining the company will continue to monitor the situation.

'They have to pay us regardless'

The Oshawa assembly plant is one of five North American plants closing at the end of the year. That means the workers sent home or told to stay away will be paid a full wage because of a contract stipulating all full-time employees must be paid for the last 16 weeks of work.

"This affected GM more than it affected us — we're already prepared for the plant closure, and now because of the contract they have to pay us regardless," Peter Levesque, who opted to go home on Wednesday morning, told CBC News.

Unifor Local 222 union representative Mike Barry said the contract negotiated by the union is protecting workers from losing money during a shutdown of the truck assembly line at GM's Oshawa plant. (Linda Ward/CBC)

Unifor Local 222 union representative Mike Barry said his main concern is keeping everyone inside the Oshawa plant happy for now.

"Our union has gone through great lengths with the company to make sure this isn't affecting us financially right now," Barry said.

"We're just standing behind our brothers in the States — they've got a big fight ahead of them, but they can do it," he added.

Both the union and GM are watching two other plants in Ontario closely, but so far the assembly plant in Ingersoll and the engine and transmission plant in St. Catharines have been unaffected by the parts shortage.

However, Jerry Dias, president of Canadian union Unifor, said workers in St. Catharines could face layoffs within days, since about 80 per cent of the engines the plant builds are destined for cars assembled in the U.S.

At the Ingersoll assembly plant, about half the engines they put in cars come from the U.S. Dias estimates they may have to halt operations within 10 days.

GM has not said how many days of parts it has in reserve.