Credit reporting agency Experian said Thursday that hackers accessed the Social Security numbers, birthdates and other personal information belonging to about 15 million people who applied for T-Mobile wireless services.
T-Mobile uses Experian to check the credit of its customers and prospective customers.
Experian said consumers who applied for T-Mobile wireless service between Sept. 1, 2013, and Sept. 16, 2015, may have had their information stolen.
Experian said it immediately notified law enforcement authorities after discovering the hack and that "there is no evidence to-date that the data has been used inappropriately."
The companies said that payment card and banking information were not affected.
"Obviously I am incredibly angry about this data breach and we will institute a thorough review of our relationship with Experian, but right now my top concern and first focus is assisting any and all consumers affected," T-Mobile US Inc. CEO John Legere said in an open letter to consumers.
There have been a string of high-profile hacks of businesses and other organizations in recent years affecting millions of people, including adultery website Ashley Madison, Sony Pictures, the insurer Anthem, retailers such as Home Depot and Target, eBay and the U.S. Office of Personnel Management.
Nearly 800 data breaches were reported last year by U.S. organizations, according to the Identity Theft Resource Center.