More than 30,000 Stop & Shop supermarket workers across three states remained on strike for a third day on Saturday, protesting what they said were unfair wages and high health insurance premiums.

The strike, by United Food and Commercial Workers International Union members working at more than 240 Stop & Shops in Connecticut, Massachusetts and Rhode Island, forced some stores to close. Union and supermarket officials could not say precisely how many.

The supermarket activated a contingency plan that included sending support-office staff members and temporary replacement workers to select locations, according to a Stop & Shop spokeswoman, Jennifer Brogan. Pharmacies and banks remained open, regardless of a store’s status, she said.

Among the workers on strike were cashiers, stockers, bakers, deli clerks and butchers. A previous three-year contract expired on Feb. 23.