June 16 (Bloomberg) -- General Motors Corp. workers ended a blockade of the automaker's Canadian headquarters over the planned closing of a truck plant as their union discussed the possibility of adding production at a car factory.

The protest in Oshawa, Ontario, which began June 4, concluded today after Ontario Superior Judge David Salmers on June 13 ordered the Canadian Auto Workers to halt it. GM is in preliminary talks to add a third vehicle at an Oshawa car plant, company spokesman Stew Low said.

GM, the largest U.S. automaker, is trying to quell labor unrest that began after it said the pickup-truck factory in Oshawa would shut by the end of 2009 as high gasoline prices shift demand to cars. GM is adding two U.S. car shifts and had already promised a second vehicle at the Oshawa car plant during a three-year labor agreement reached with the CAW on May 15.

``Now is the time to focus on discussions on new product mandates for Oshawa and support for affected employees,'' Low said.

The Oshawa car factory, part of a production complex with the pickup facility, already has three shifts producing Chevrolet Impala and Buick Lacrosse and Allure models. The plant is slated to begin making Chevrolet Camaros later this year, and the new line for that car can build as many as three models, with either front- or rear-wheel drive, Low said.

The union has contended that closing the Oshawa pickup plant violates the May 15 agreement. GM has said the contract allowed for such closings if market conditions changed. The Oshawa pickup plant is one of four truck factories being shut.

CAW President Buzz Hargrove and GM Chief Executive Officer Rick Wagoner met June 6 in Detroit, and Hargrove said then that he was unable to win a reprieve for the pickup plant. The union said the shutdown would eliminate 2,600 jobs.

U.S. sales of pickups, SUVs and vans fell 22 percent this year through May for GM, and 16 percent for the industry. The light trucks accounted for 61 percent of sales last year at GM, which hasn't had an annual profit since 2004.

To contact the reporter on this story: Jeff Green in Southfield, Michigan at jgreen16@bloomberg.net

Last Updated: June 16, 2008 09:35 EDT