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Marriott International said Tuesday that names, mailing addresses, loyalty account numbers and other personal information of an estimated 5.2 million guests may've been exposed in a data breach. This is the second major security incident to hit the hotel group in less than two years.

Marriott said it spotted that an "unexpected amount" of guest information may've been accessed at the end of February using the login credentials of two employees at a franchise property. The hotel group said information exposed may include names, addresses, emails, phone numbers and birthdays as well as loyalty account details and information like room preferences.

Marriott said the investigation is ongoing but that it doesn't believe credit card numbers, passport information or driver's license numbers were exposed.

In November 2018, Marriott announced that hackers compromised the reservation database for its Starwood division in one of the largest data breaches ever. Following an investigation, the hotel group said hackers accessed the records of up to 383 million guests and stole more than 5 million passport numbers.

The company is sending emails to guests impacted by this latest breach and offering a year of free personal information monitoring.

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