CHICAGO (CBS) – It’s been a bad month for the Chicago Police Department, and it’s about to get worse, perhaps even much worse. CBS 2 has learned that in addition to the five policemen taken off the street last week, four more are under investigation.

The matter is now the focus of an internal police investigation.

Police sources CBS 2’s Dana Kozlov spoke with Thursday afternoon confirmed those four police officers were stripped of their police powers Wednesday.

The officers are all from the same district. They’ve been placed on administrative duty and the police Internal Affairs Division is leading the investigation.

Police officials confirmed the action but would not say what district the officers’ work out of, or what the possible wrongdoing is.

The Internal Affairs investigation is a noteworthy distinction because that means the probe started within the police department, and could focus on anything from on-the-job misconduct to possible illegal activity.

That’s different from an Independent Police Review Authority investigation, which handles allegations made by citizens.

This comes just two weeks after a Chicago police sergeant and four officers were removed of their duties over allegations of police brutality.

Sources say this case is not related to that one.

Fraternal Order of Police President Mark Donahue says he hasn’t heard anything about this.

And again, department brass is not commenting on why they are under investigation.