The Wawa convenience store chain says a data breach may have collected debit and credit card information from thousands of customers.

Pennsylvania-based Wawa Inc. said Thursday that its information security team discovered malware on its payment processing servers on Dec. 10 and stopped the breach on Dec 12. The company believes the malware was collecting card numbers, customer names and other data as early as March 4.

The company said it doesn't yet know how many customers were affected. Wawa said it's also unaware of any unauthorized use of credit cards as a result of the breach.

The breach affected all of Wawa's 850 locations, which stretch along the East Coast from Pennsylvania to Florida. In-store payments and payments at fuel dispensers were affected, but ATM machines were not.

Wawa says it's notifying customers and offering free credit card monitoring and identity theft prevention services to anyone whose information may have been collected. Police are investigating, and the company has also hired a forensics firm to conduct an internal investigation.