The facilities made some trucks, but those trucks are also made at in Mexico.
She now faces an uncertain future, not knowing whether the plant will close for good or if there's a chance it could find another use.
Unifor, the union representing more than 2,500 workers at the plant, said it has been told that there is no product allocated to the Oshawa plant past December 2019. GM now employs roughly 54,000 workers in North America.
The company said the changes were the results of shifts in consumer demand, with SUV and pickup truck sales increasing while sedan sales stall.
A spokeswoman for GM Canada said Sunday that the company had "no news or comment tonight" and would not be commenting on speculation.
GM said it will reduce its salaried workforce by 15%, including a quarter of the company's executives.
"The actions we are taking today continue our transformation to be highly agile, resilient and profitable, while giving us the flexibility to invest in the future", Mary Barra, GM chairman and CEO, said in a news release.
Barra said tariffs on imported aluminum and steel have hit the company, but she stopped short of saying they had anything to do with the restructuring.
"The closure of this plant will have a ripple effect like we have never seen before".
"We're going to have to use all of the power of government to make sure that General Motors understands that they're not betraying this country again", he said.
The closures come as North American automakers feel pressure from USA tariffs on imported steel and aluminum.
General Motors Canada will be announcing the closure of all operations in Oshawa, Canada on 26 November, multiple anonymous sources told CTV News Toronto. "We think it's appropriate to do it while company is strong and the economy is strong". Dias said to cheers from union members.
"The PC government is also asking the federal government to work with their US counterparts to remove all tariffs so that impacted auto parts suppliers can remain competitive after the Oshawa Assembly Plant closes its doors".
"They're gone; they're done".
Scheer says the closure is devastating to thousands of families in southern Ontario and the government needs to immediately explain how it will help them and protect other manufacturing jobs in Ontario.
In October, Export Development Canada, the national export credit agency, showed there was an outstanding loan to GM Corp. for more than $1 billion.
GM jumped as much as 7.9 percent to US$38.75, the highest since July, as of 12:20 p.m.in NY trading.
While General Motors has dramatically reduced production and assembly in Canada, it announced a plan in June 2016 to hire about 700 engineers to expand research into self-driving cars and other technology.
The company says 5,901 hourly employees and 804 salaried employees work at these plants.
The auto giant is reportedly preparing for the next economic downturn, shifting trade agreements under the Trump administration, and potential tariffs on automobiles.
The US$6-billion in savings includes cost reductions of US$4.5 billion and lower capital expenditure annually of nearly US$1.5 billion, GM said. The affected facilities build cars that will not be sold in the U.S. after next year.
The plant closure announcement was confirmed late Sunday by an official familiar with the decision.
GM production in Oshawa began in 1953 and peaked in the 1980s, when the company employed 23,000 people in the city.