A pedestrian walks past an AT&T store in New York, USA

Scott Mill | CNBC

AT&T announced Saturday that it is investigating an incident two weeks ago that resulted in millions of customer data being published on the dark web, a part of the Internet that can only be accessed through special software.

The company has reset the passwords of 7.6 million current users who were affected and said it is actively contacting those customers, along with 65.4 million former account holders whose data was also compromised.

“To date, this incident has not had a material impact on AT&T’s operations,” the company said in a press release Saturday.

AT&T’s preliminary review found that the leaked data was from approximately 2019 or earlier and included personal information such as names, home addresses, phone numbers, dates of birth and Social Security numbers. The data set does not contain personal financial information or call history.

AT&T encouraged consumers who would receive an email if they were affected to create fraud alert accounts and monitor their account activity and credit reports. The company has not yet identified the source of the leak.

In February, AT&T customers experienced hours cellular network outage, which the company clarified was the result of a system issue, not a cyberattack. The company’s CEO, John Stankey, later apologized for this incident and provided customer credits to those affected.

CLARIFICATION: AT&T says it is investigating an incident two weeks ago that resulted in millions of customers’ data being posted on the dark web. It is not clear if there was a breach in the system.