By Brad Segall

KING OF PRUSSIA, Pa. (CBS) — Ten more people have been charged in an ongoing investigation into alleged criminal activity inside the local office of the Pennsylvania Department of Transportation.

State prosecutors say taxpayers were defrauded of more than $5 million.

Officials say the latest arrests stem from a widespread overbilling scheme in which Penndot managers in District 6 , which serves the five-county Philadelphia area, were encouraging contractors to fill out fraudulent timesheets and mileage reports in exchange for kickbacks.

The grand jury presentment also details a pattern of nepotism and cronyism that resulted in some getting their jobs even though they weren’t qualified.

“The overall investigation has uncovered abuses throughout the whole district,” says Pennsylvania chief deputy attorney general Erik Olsen.  “This overbilling of overtime did reach out into the suburbs but was primarily in the city of Philadelphia.”

Olsen says the investigation is far from over.  Every door they open, he says, leads to at least two or three other doors.

The two former Penndot managers at the center of the scheme are Alex Morrone and William Rosetti.  All the defendants were released on $200,000 unsecured bail.