CHICAGO HEIGHTS, Ill. (CBS) — The United States Post Office Inspector General is investigating a fraud scheme that victims believe revolves around a south suburban post office.

As CBS 2’s Mike Puccinelli reported, investigators believe someone has been ripping off individual customers and area entrepreneurs at the Chicago Heights Post Office with checks that all may have come through the building.

Now, some of the victims are speaking out for the first time.

At work at Enzo’s Beef and Sausage, owner Kyle Hallberg was on the phone with investigators from the U.S. Postal Service Office of the Inspector General. And the postal inspectors were not looking for a famous beef sandwich.

The call was because Hallberg was the latest victim of check fraud in the south suburb. His company’s bank account was drained of all its money Tuesday morning and had a balance of -$400.

He said $15,000 was gone.

And Hallberg said he’s not alone. Fraudulent checks were also written against Eagle’s Liquors right next door, Country Squire Foods just up the street, and at least one other small business.

“I think it happened at the Chicago Heights Post Office – that’s the common denominator,” Hallberg said.

And it’s not just small businesses that are being affected. A 79-year-old great grandmother was also ripped off after she put her check to the gas company in a mail slot.

“I feel like I was being picked on,” she said.

The woman did not want to say her name, but did want to warn others about how their small check for $160 ballooned into one for nearly $5,000.

The check was made out to somebody named Melody Lenoir – whom the woman said she does not know and to whom she most definitely did not write out a check for $4,990.

She and Hallberg both expect to get their money back from their banks. But it will be harder to restore their trust in the Post Office.

“I’m not putting anything in the mailbox that’s going to the Post Office,” the woman said.

“That will be the last,” Hallberg added. “I won’t do it again.”

We reached out to USPS officials in Chicago Heights and also nationally. As of 6 p.m. Tuesday, we had yet to hear back.

Mike Puccinelli