By Jermont Terry

CHICAGO (CBS) – For weeks, there were constant ripoffs from mailboxes in the West Loop.

Residents just couldn’t figure out how thieves were getting in.

Now, a woman is behind bars, facing federal charges. Thanks to a traffic stop by Chicago police, CBS 2’s Jermont Terry reports.

For those living in the West Loop the arrest is a great start. However, the looming question: who else was in on this crime spree.

It’s not that simple for people in this neighborhood to get mail, especially with thieves gaining access to secure buildings by using a U.S. postal worker master key.

Neighbors were forced to install a digital key pad, mainly because crooks kept stealing mail, using the key postal workers should only carry. But clearly these were no mail carriers.

“It was such a violation to have someone pry open the mailbox,” one woman said. “It’s ridiculous.”

These thieves walked away with personal information, too.

“Our neighbor had her identity stolen,” a resident said. “These people had taken out credit cards and mortgages.”

CPD arrested Aliyah Massari.

Aliyah Massari

When officers stopped the 24-year-old during a traffic stop in the West Loop, they say they found large amounts of stolen mail, and get this, five sets of those mailbox keys

Yet the video clearly shows more than one woman going into the buildings–leaving many to wonder whether somebody from the postal service is involved.

Police and postal service investigators aren’t saying if the woman arrested is the ringleader, or who else may be involved.