If you stayed at a Marriott company hotel over the past few months, you will want to keep an eye on your personal information.

Company officials announced an investigation into a hack of a guest reservation database at its Starwood division. It is said that the breach could be one of the biggest in history.

Officials said the hack targeted 500 million guests and that the hackers were able to get passport numbers and credit card information of some guests, Bloomberg reported.

Company officials said that its internal security tool alerted them about a potential breach on Sept. 18, but Nov. 19 was when Marriott could decrypt the information to find out what exactly was taken, The Wall Street Journal reported.

>> Read more trending news

About 327 million guests had a combination of name, mailing address, phone number, email, passport number, Starwood Preferred Guest information, birthday and gender accessed by the hackers, Reuters reported.

Reuters reported Marriott International said the unauthorized access started in 2014 and that the hackers copied and encrypted information.

Marriott bought Starwood in 2016.
Company officials said they have contacted law enforcement and have started to notify regulatory authorities, Bloomberg reported.

"We fell short of what our guests deserve and what we expect of ourselves. We are doing everything we can to support our guests, and using lessons learned to be better moving forward," Chief Executive Arne Sorenson said via a press release to The Wall Street Journal.