As many as 5.2 million people may have been affected by a data breach to hotel chain Marriott International’s (MAR) property system.

The company said it identified a breach where guest information may have been accessed, including login credentials by two franchise employees. Marriott said the incident started in mid-January when it immediately began an investigation.

While the investigation is ongoing, Marriott said it has no reason to believe that the information accessed included passwords or PINs, payment card information, passport information, national IDs, or driver’s license numbers.

The information that Marriott believes was accessed includes contact details, loyalty account information, additional personal details such as gender and birthdates, other loyalty program information, and lodging preferences.

Marriott has sent emails to all the hotel guests involved in the breach and has set up the website, www.mysupport.marriott.com, along with call center resources to assist these affected individuals.

Shares of Marriott International stock was down 0.34% as of 2:23 p.m. EDT on Tuesday.

Marriott said it does have cyber insurance to cover these incidents, but it does not believe the total costs will be that significant.