The ATF has been investigating since March when an apartment building fire left nine people homeless in Jeannette, about 25 miles east of Pittsburgh just off the Route 30 corridor. At the time, Jeannette fire officials said it was the city's 12th arson or suspicious fire since October.
ATF officials say they'll announce details of their investigation later Wednesday, and that the investigation is continuing. ATF investigators are still looking into 11 other fires, and say the evidence has led them to investigate fires as far back as 2008.
Many of the burned buildings were vacant.
ATF officials say the suspects include on juvenile and five adults.