TORONTO (Reuters) - Production resumed at General Motors’ assembly plant in Oshawa, Ontario on Friday afternoon, ending a near three-hour standstill, after striking workers at seat supplier Lear Corp returned to work, the autoworkers’ union said.

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After Oshawa exhausted its on-hand supplies of seats, production came to a stop around 12:30 p.m. EST (1730 GMT), GM Canada said. It was unclear if both car and truck assembly was affected and what impact the stoppage had on daily production, said spokesman David Paterson.

Full production of Chevrolet Silverado and GMC Sierra trucks resumed at the Oshawa plant at approximately 3:10 p.m. EST (20:10 GMT), said Unifor Local 222 President Colin James.

More than 200 Lear workers walked off the job on Friday, but the next shift went to work at 2:30 p.m. EST (19:10 GMT), ending the strike, James said.

Oshawa produces about 250 Cadillac XTS and Chevrolet Impala cars daily, on one shift, and approximately 450 GMC Sierra and Chevrolet Silverado trucks daily, on two shifts.

GM had a sizeable 149-day supply of Silverado trucks in the United States as of February 1. The automaker also says that production of its new Silverado/Sierra trucks from Fort Wayne and Silao, Mexico has increased to the point where more than half the trucks sold are new models.

The strike at Lear, which has 350 unionized workers, is the latest measure in a Unifor campaign aimed at convincing GM to extend Oshawa production to September 2020, when the current contract expires. Under a broad restructuring announced in November, GM said it will close Oshawa by end-2019 and has repeatedly said it will not change that decision.

The Oshawa plant operates on a just-in-time delivery system, keeping a limited supply of bulky commodities like seats on hand, said GM Canada spokeswoman Jennifer Wright.

Unifor represents 2,600 assembly-line workers at GM Oshawa and 1,800 workers at plants supplying GM’s Oshawa operations.

“The message that we’re sending is that it’s not just about General Motors’ workers. All the suppliers, including Lear Whitby, are impacted by a potential closure,” James said.

This week, GM reported a market-beating quarterly profit, lifted by high-margin trucks and cost cutting.

Large pickups, like the Silverado, generate at least $17,000 per vehicle in pre-tax profit, according to GM investor disclosures.