While others were decking the halls, thieves working Boston’s western suburbs were trying to line their pockets for Christmas.

The Mansfield-based Roche Bros. Supermarkets, which owns 20 stores under a variety of names, reports that an employee of their Sudbury Farms location “noticed an inconsistency” at a self-checkout lane in the store.

Store management checked it out and found two credit card skimmers. Those are devices laid on top that look nearly identical to legitimate credit card machines. But, they capture the financial information on a card’s magnetic stripe.

Thieves would then come back and retrieve the ill-gotten financial information and make off with somebody else’s credit.

“Roche Bros. Supermarkets immediately took steps to secure all registers at all stores and upon deeper inspection over the holiday break credit card skimmers were found on self-checkouts at 4 more locations,” the company wrote on Tuesday. “Law enforcement has been contacted.

The locations affected are: the Sudbury Farms locations in Sudbury and Needham, the Brothers Supermarket in Weston, and the Roche Bros. Supermarket locations in Wellesley and Natick.

The company says that customers who shopped at these locations on Christmas Eve or the days before could have been impacted but that “there has been no confirmation that any customer data has been compromised.”

Police in Concord, N.H., who are investigating skimmer activity in their own jurisdiction, said last month that customers should watch out for a “telltale sign” of a possible skimmer scam: that the card chip reader slot is inoperable and appears “jammed,” forcing customers to swipe the card so the information can be stolen.

An example of a credit card skimmer, with the top, public-facing portion seen at left and its reverse seen at right. (Collage, Flint McColgan / Boston Herald, composed of courtesy photos from Concord PD)