By Dana Kozlov

CHICAGO (CBS) — One key fits all – and it’s a big problem for residents of a Chicago condo building where people keep having their mail stolen.

As CBS 2 Political Investigator Dana Kozlov reported Wednesday night, thieves have been captured on surveillance video using a key that is supposed to be Post Office property only.

READ MORE: Jury Begins Deliberations In Jussie Smollett Trial After Closing Arguments Conclude

Postal carriers use a master key to access mailboxes all at once in multi-unit buildings. So when the residents of a Clybourn Corridor area condo building caught two non-residents rifling through all 40 mailboxes, it sounded alarms.

“Clearly, they have access through a master postal key. It’s the only way you can get in if you don’t have a key fob to our building,” said condo board member John Crenshaw. “If you had a key fob to our building, we would be able to track where that fob came from.”

Crenshaw said four neighbors have reported missing mail.

“When I came back about 5 o’clock, it was empty,” said Marilyn Goldman.

Goldman said her mail was taken out of her box one recent Sunday and moved. A man caught on the surveillance video is the suspected culprit.

READ MORE: Chicago Weather: Turning Cloudy Wednesday Night

Goldman has no idea if anything was taken.

“‘How were they able to do that?’ is really what my thought was,” she said.

Their building is not easy to enter. The front door is locked with a buzzer, and the mailroom is locked too.

Meanwhile, this is just the latest in a string of stories we’ve done on thieves using a master postal key to steal mail from apartment buildings. Crenshaw said victims have filed complaints with the Post Office.

“I would like to se USPS take responsibility somehow,” Crenshaw said.

A Post office spokeswoman said she has given the information to the theft department, and all complaints are investigated.

MORE NEWS: Aurora’s Snow Removal Program Returns For Senior Citizens And Residents With Disabilities

Kozlov also asked for a status update on the investigation and how someone might be able to get a hold of a master key. She was still waiting for answers to those questions Wednesday night.