AT&T is investigating a leak earlier this month that dumped millions of customers’ data, including personal information such as social security numbers, on the dark web.

The company said the leak happened roughly two weeks ago and it launched “a robust investigation supported by internal and external cybersecurity experts.”

“Based on our preliminary analysis, the data set appears to be from 2019 or earlier,” AT&T said in a statement Saturday.

It affects about 7.6 million current customers and about 65.4 million former customers.

AT&T said it is looking into whether “the data in those fields originated from AT&T or one of its vendors.” Currently, the company does not have evidence of unauthorized access to its systems resulting in exfiltration of the data set.

The telecommunications company, one of the most popular wireless carriers, said it is reaching out to the customers affected and has reset their passcodes. They are also offering free credit monitoring through Equifax, Experian, and TransUnion.

“As of today, this incident has not had a material impact on AT&T’s operations,” the company said.