BALTIMORE (WJZ) — A data breach may have exposed Under Armour employees’ names, Social Security numbers and salary information.

An unencrypted thumb drive containing that information was lost in the U.S. Mail on or about April 12 by its auditing firm, PWC.

“PWC is committed to protecting its clients’ confidential information and is working closely with its client to provide protective safeguards to those individuals whose information was lost. The firm deeply regrets that the information was lost in transit to a PWC facility and is conducting a thorough internal investigation into these events to determine how PWC’s client security protections were breached,” said Jude Curtis, PWC Chief Ethics and Compliance Officer.

There is no evidence that the employee information has been compromised. Employees will receive free credit monitoring and identity protection, including identity theft insurance, for a year.

In a memo, Under Armour officials said they were working with PWC and authorities but so far, the thumb drive hasn’t been found.

“We are undertaking a thorough review of this incident to help ensure that it will not be repeated,” the memo said.

Under Armour employs about 5,400 people worldwide.