The company is directly notifying affected customers.

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The nation’s third-largest wireless carrier said late Thursday that it had discovered a data breach potentially affecting some of its customers’ account information.

No financial data was stolen in the incident, the company said, but some personal details such as customer names, email addresses, phone numbers and account numbers may have been compromised.

In a statement on its website, T-Mobile said it uncovered the hack on Monday. The company “promptly reported it to authorities” and shut down the attack.

Affected T-Mobile customers are being notified directly by the company by a text message. Impacted customers can call customer service if they have questions, but the company isn’t requiring them to change any account security, though the T-Mobile statement notes “it’s always a good idea to regularly change account passwords.”

About 3 percent of T-Mobile’s 77 million customers were affected, the company said in a statement to The Washington Post. That translates to roughly 2 million customers.

The attack came through a web-based program, and T-Mobile discovered it almost immediately, a spokeswoman said Friday. No company information was exposed, she said.

Related:

Read more about protecting your sensitive personal information, data collection and security breaches. Plus, what you need to know about privacy settings.

Information from Seattle Times staff is included in this report.