NEW YORK (CNN/Money) - Ford Motor Credit Co. is warning 13,000 people to be aware of identity theft after the automaker found hackers posed as employees to gain access to consumer credit reports from credit reporting agency Experian.

The company explained in a letter that was sent to the 13,000 people, only 400 of whom were Ford credit customers, that the hackers used an authorization code from Ford Motor Credit to access a database used by Experian to download customers' personal information.

Ford Credit said it contacted Experian after the automaker received a phone call about an unauthorized credit check in February, which appeared as though it was made by Ford Motor Credit.

The company said it alerted the FBI soon after that, and the letters were sent to consumers beginning in late April.

The credit unit of Ford said it "is concerned about this unauthorized activity," and it is currently cooperating with the FBI and Experian as they conduct a thorough investigation into this issue.

The company also urged the victims to contact the credit bureaus to obtain a credit report and review it for any unauthorized credit inquiries or other incorrect information.

Ford Credit also has a hotline dedicated to anwering customers questions on this matter, and the toll-free number is 1-888-838-8176. For those who wish to contact Experian, the number is 1-877-828-1530.