T-Mobile, a US telecom company, announced on Thursday that it had recently experienced a hack that compromised the information of 37 million users.

The SEC revealed that the company’s computer system had been infiltrated on January 5 by a bad actor who was able to steal information without authorization.

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After discovering the hack’s source, it was fixed within 24 hours, the service provider said, adding that it believes everything else in its system was not affected.

The company later concluded that the incident most likely started around November 25. According to the details, the contents of the T-Mobile hack include email addresses, phone numbers, birth dates, addresses, and account details.

The company clarified that t does not include bank or Social Security cards information, tax data or passwords.

“Customer accounts and finances were not put at risk directly by this event,” the Deutsche Telekom-owned company said. The company further said that affected customers will be notified and an internal investigation is under way, and it will be ongoing.

“We may incur significant expenses in connection with this incident,” T-Mobile said.

The most recent hack comes after an incident around two years ago in 2021 that affected the personal data of 76.6 million Americans.

Last summer the company paid $350 million to settle the plaintiffs’ class-action lawsuits to spend $150 million on cybersecurity and data protection for the next two years.