ST. LOUIS (KMOV) – If you use a credit card to pay for gas at the pump, listen to this: thieves are stealing account numbers in the St. Louis area.

There are already 21 victims, and the number is growing.

The worst part? No one seems to know how the account numbers are getting stolen.

All of the victims have two things in common: they recently used a debit card at a gas station, and they are all members of the Altonized Community Federal Credit Union in Alton, Ill.

President Rick Sebold said the security breach isn’t at the credit union.

“Somebody has hacked into somebody's system. We know for a fact it wasn't our system,” he said.

The culprits are using the stolen information at gas stations in the Orlando area. Some of the victims recently bought gas at stations in West Alton, Ill., including BP.

A company spokesperson said the breach isn’t on their end either.

The credit union is encouraging people to check their accounts and call 800-554-8969 if they notice any problems.