Lodgers at Holiday Inns, Marriott and Renaissance hotels may have had their payment card details compromised following a new disclosure of suspected point-of-sale device attacks.
White Lodging Services, a hotel management company, warned it suspects point-of-sale systems at restaurants and lounges on 14 of its properties were compromised between March 20 and December 16 last year.
Guests who did not use their card at restaurants and lounges, as well as those who used their room account for purchases from those outlets, were not affected, it said.
The Merrillville, Indiana-based company said it manages hotels under agreement with hotels owners and is a separate entity from the specific hotel brands it operates.
The company said it has contacted federal law enforcement and initiated a forensic review of its properties. It runs more than 169 hotels in 21 US states.
"We deeply regret and apologise for any inconvenience caused by this incident and remain committed to protecting all information entrusted to us by our guests," it said.
White Lodging told the New York Times last week it was investigating a potential security breach, covered in a report from security writer Brian Krebs.
It is the latest company following Target, Neiman Marcus and Michaels to either confirm or disclose a suspected breach, as security experts warn dozens of companies worldwide may be affected.
The unfolding disclosures have drawn the attention of the US Congress. Tomorrow the House Energy and Commerce Committee is scheduled to hear from senior executives from Target and Neiman Marcus along with the US Secret Service about how data breaches can be prevented.
Attackers are planting malicious software, known as "RAM scrapers," on POS devices, which capture unencrypted card details after a customer has swiped a card, defeating other security measures in place intended to protect sensitive details.
White Lodging said customers' names as printed on credit or debit cards, the card numbers, the cards' security code and expiration dates may have been unlawfully accessed.
Financial institutions have reissued some payment cards and are monitoring other credit and debit cards for unauthorised activity, the company said.
White Lodging listed the 14 affected facilities in the states of Illinois, Texas, Pennsylvania, Colorado, Texas, Indiana, Virginia, Kentucky, Florida and Colorado. It includes seven Marriott, two Holiday Inn and two Renaissance hotels, plus one Sheraton, one Westin and one Radisson hotel.
At its Radisson Star Plaza site in Merrillville, a property management system used at the front desk may have been affected in addition to a point-of-sale system, White Lodging said.
The company also runs upmarket hotels such as Hilton, Hyatt and Intercontinental with others bearing the Preferred Hotel Group, Starwood Hotels and Resorts and Carlson Rezidor Hotel Group brands.