A labor dispute involving truck drivers and mechanics for Shaw’s supermarkets in Maine led to a strike Monday that the grocery chain vowed to resolve this week.

A representative of the Teamsters Local Union No. 340 in South Portland issued a statement early Monday saying the workers were going on strike as of 5:30 a.m.

He said most of the the striking workers are drivers who deliver dry goods and groceries from a distribution center in Wells to 122 Shaw’s stores around New England. The others are mechanics in Scarborough who maintain the trucks.

About 70 workers in all are on strike, said Joe Piccone, business agent for the Teamsters local.

“The parties have met over 20 times since Oct. 2020 when the current contract expired,” Piccone said in a statement. “Since February 2021, the company has stated that they have a counter-proposal but are unable to present it because they currently have no one with authority to negotiate available.”

Piccone said the lawyer representing Shaw’s and its parent company, Albertsons Companies Inc., quit this year, and that the two sides have not met since February.

He said the main issues over the contract pertain to how much work can be subcontracted and the amount the company contributes to retirement accounts.

Shaw’s issued a statement Monday afternoon saying it had been bargaining in good faith with the union on a new labor agreement and would be returning to the bargaining table this week.

“Since August 2020, we have participated in approximately 20 bargaining sessions, including one-quarter of these sessions with a federal mediator in attendance,” the company’s statement said. “We remain committed to reaching an agreement that recognizes the tremendous value our associates provide to our company’s current and future success.”

Jim Kelly, a driver with Shaw’s supermarkets who is on strike, looks at the driver of a truck leaving the Shaw’s distribution facility in Wells on Monday. Gregory Rec/Staff Photographer

Shaw’s said it has a proposal to offer that includes contract improvements, “yet it was not presented to the membership for a vote for approval.”

“We look forward to our employees returning to work this week,” it said.

Piccone said company officials told him earlier this year, “We have a great offer, but we can’t show it to you, and we’re working on getting someone with authority who can.”

“They’re promising us it’s awesome, though,” he said.

Piccone said striking Teamsters in Wells were picketing at the entrance to the distribution center Monday and delaying, but not blocking, trucks from entering and leaving. He said the company was using truckers from a distribution center in Massachusetts, subcontractors and other trucking lines to replace the striking workers.

There have been sporadic labor disputes involving supermarkets in Maine over the past decade.

Workers at a Hannaford distribution center in South Portland staged a 24-hour walkout in 2018 during negotiations over a contract at that site. The two sides agreed about a month later to a new contract that called for three years of wage hikes for workers and maintenance of health care coverage, but lower starting wages for new employees.

The other major labor action in the industry in Maine was in 2014 at the Market Basket store in Biddeford, where workers staged demonstrations, but didn’t walk off the job, to protest a corporate shake-up that resulted in the ouster of CEO Arthur T. Demoulas, who was popular with the workers. Some workers in Massachusetts went on strike and many customers stopped shopping at Market Basket stores in a show of support for Demoulas.

Demoulas was eventually able to engineer the purchase of the half of the company that he didn’t own before the dispute began, and workers and shoppers returned later in the year.