Webster Five Bank in Oxford is on high alert after it learned that a number of its customers’ debit cards were compromised this past weekend.

Joe Radovanic, senior vice president of retail banking, said Webster Five had not yet determined how many of its customers were affected by the scam. Webster Five learned about the fraud on Sunday night when its fraud monitoring system picked up suspicious activity in New York City and Boston.

“Our fraud detection system was able to catch this pretty early, so we were able to put some blocks on different types of transactions, so we were able to reduce the amount of fraud,” Radovanic told Banker & Tradesman today.

The bank traced the fraud back to skimming devices placed on Webster Five ATMs in Dudley and Webster, likely earlier this summer, Radovanic said. The devices were placed on the machines after business hours and removed before the start of business the next day; the scheme affected anybody who used those ATMs during that time.

Webster Five has begun reimbursing affected customers and reissuing cards. The bank is also cooperating with law enforcement in an ongoing investigation.