Chick-fil-A, Inc. informed customers of suspected “fraudulent activity” on some customers’ mobile app accounts and has announced an investigation to determine the source.

“Chick-fil-A is aware of suspicious activity on some of our customers’ Chick-fil-A One accounts,” the company said in a statement Thursday. “While we are still investigating what happened and how certain customers became subject to this fraudulent activity, this is not due to a compromise of Chick-fil-A Inc.’s internal systems.”

The beloved chicken sandwich retailer emphasized that its internal systems have not been compromised and said the company has taken steps to secure affected accounts and enhance its security protocols.

“Chick-fil-A is committed to protecting our customer’s data and we are working quickly to resolve the issue. Please reach out to Chick-fil-A CARES online or by calling 1-866-232-2040 to report any suspicious account activity,” the statement read.

In a message to app users, Chick-fil-A advised customers to change their account passwords. 

“We have already taken precautions to further secure the affected member accounts and are continuing to review the situation and enhance our security protocols where appropriate. This activity is not the result of any compromise to Chick-fil-A’s internal systems,” an email sent to customers on Friday states.