Workers at some Starbucks stores started a five-day strike Friday in three U.S. cities, including Chicago, to protest lack of progress in contract negotiations with the company. S

Workers at more than a dozen Chicago area Starbucks were on strike Christmas Eve, union organizers said, as baristas escalated a national walkout that began in three cities, including Chicago, on Friday.

A five-day strike by Starbucks baristas had closed 59 stores as of Monday afternoon, according to the union organizing the workers.