PITTSBURGH — Federal prosecutors and the FBI are set today to announce dozens of arrests in what they’re calling a series of “overlapping and interrelated heroin distribution networks” in southwestern Pennsylvania.

The arrests are not believed to be linked to a series of more than 20 overdose deaths in the Pittsburgh-area from people using heroin laced with fentanyl, a powerful synthetic painkiller.

Still, roughly 40 people were expected to be charged, and arrests were reportedly occurring today.

U.S. Attorney David Hickton and Assistant Special-Agent-in-Charge Patrick Fallon of the Pittsburgh FBI office have scheduled an afternoon news conference to details the charges and arrests.