The Hyatt hotel chain became the latest in a series of hotel companies to get hacked, with the company announcing yesterday that it had discovered credit-card stealing malware in its payment system, Reuters reports. Last month, Hilton and Starwood both announced data breaches, and the month before that the Trump Hotel Collection disclosed that malware may have been active for more than a year.

Hyatt hasn’t said how many customers or hotels were affected, only saying that an investigation was ongoing and customers should look for suspicious charges. Hyatt also told Reuters that the attack was discovered on November 30th.

“We recently identified malware on computers that operate the payment processing systems for Hyatt-managed locations,” Hyatt said in a statement posted online. “As soon as we discovered the activity, we launched an investigation and engaged leading third-party cyber security experts.”