A fire at the former Solon Manufacturing Plant over the weekend was most likely intentionally set.That’s according to Ken Grimes from the state Fire Marshal’s Office.He says now they’re looking into who is responsible. They are not releasing how the fire was started.The plant has been vacant since 2003. Sunday’s fire was the seventh there in two years. Investigators say a few of those fires were accidental while some were intentional.About 40 firefighters responded from Solon, Bingham, Anson, Madison and East Madison. No one was injured.