Target, the discount chain, says about 40 million credit and debit cards may have been affected by a data breach.
The company said Thursday the theft happened in stores, not online, and accounts may have been impacted between November 27 and December 15.
Target says it immediately reported the matter to authorities and financial institutions and an investigation is underway. The company's advising customers to check their statements carefully.
There are 1,797 Target stores in the U.S., including one in Stamford, and 124 in Canada.
Any unauthorized activity should be reported. Call Target Corp. at 866-852-8680.