Unifor members at the General Motors auto assembly plant in Ingersoll, Ont., went on strike at 11 p.m. ET Sunday after the union failed to reach a tentative agreement with the carmaker.

The union was in talks with GM about the company's decision to cut more than 400 jobs and shift some production to Mexico. The carmaker had originally axed 625 jobs, but GM said Monday that number was reduced after retirements and buyouts.

"I would say the biggest issue is job security about the [Chevrolet] Equinox," said Unifor's Local 88 plant chair Mike Van Boekel.

"We're looking for a letter to guarantee that the work will stay here."

In July, GM stopped production of its Terrain sport utility vehicle model in Ingersoll, and 100 per cent of the volume was moved to Mexico, resulting in the layoffs.

A central priority for the union is a commitment from the company to designate the CAMI plant as the lead producer of the Chevrolet Equinox, Unifor said in a statement.

Equinox a top seller 

The Equinox is one of GM's most popular vehicles, with worldwide sales of compact SUV's having spiked 49 per cent in the past five years.

The car company has been running at maximum capacity with three rotating shifts at the CAMI plant to keep up with demand. In a statement, GM said it needed to adapt its "manufacturing plans to extend beyond one facility to meet this growing demand." 

The CAMI plant now only produces the Equinox, which is also manufactured in Mexico.

Unifor had blamed the North American Free Trade Agreement and Mexico's cheaper labour costs for the job losses, which it called unjustified given strong sales of the Chevrolet Equinox crossover and Terrain sport utility vehicle assembled at the southern Ontario plant.

CAMI Automotive

GM's CAMI facility in Ingersoll, Ont., produces the popular Chevrolet Equinox and GMC Terrain. (Canadian Press)

"Every member understands the importance of reaching a deal that secures production, and what that means to our families and the community," said Van Boekel, Local 88 chair at the CAMI plant.

Widespread effect

The union anticipates a significant economic ripple effect on the automotive sector, including GM's other operations. 

"It could be dramatic: they informed us the GM [propulsion] plant in St. Catharines would be down on Tuesday," Van Boekel said.

GM spokesperson Jennifer Wright offered reassurance, however, that the company is not anticipating slowdowns at that plant or at the Oshawa Assembly Plant where the Chevrolet Impala and Cadillac XTS are built. 

The chance of prolonged job action at the CAMI plant has already created anxiety for local automotive manufacturers supplying the plant, as well as for people in the small town of Ingersoll.

"[The strike] affects everyone," said Lori Perkins who works for a Autrans Corp., an engine supplier located across the road from CAMI. 

"From our fast food people to our grocery stores to what we can afford. It affects everybody."

Securing jobs was the key to a collective agreement to replace the one expiring in September between GM and the 2,800 plant workers, Unifor president Jerry Dias said in February.

GM employees at CAMI

2800 GM employees produce the popular Equinox at the CAMI plant in Ingersoll, Ont. (Kate Duninski/CBC)

General Motors issued a statement after the workers walked out, saying the company had made positive progress on several issues over the past weeks.

"We encourage Unifor to resume negotiations and to continue working together to secure a competitive agreement," the statement said. 

With files from Reuters