Stop & Shop workers in southern New England walked off the job Thursday, after more than 31,000 employees last month authorized their labor leaders to call for a work stoppage amid increasingly strained contract negotiations.

The United Food & Commercial Workers union said in a statement that the walkout began in the afternoon.

“Today, at 1:15 pm, the United Food & Commercial Workers Local 1445 members who work at Stop & Shop will be walking off their job,’’ the release said. “At the same time, UFCW Members at Locals 328, 371, 919, and 1459 will be walking off their jobs at Stop & Shop stores in Connecticut, Massachusetts, and Rhode Island.’’