YOUNGSTOWN — What first appeared to be a rubbish fire turned out to be a firebombing at 434 E. Marion Ave. on the South Side late Tuesday night. Firefighters said an accelerant had been thrown against the side door of the house. A man said he and three friends who were house sitting heard a noise at10:40 p.m. then saw a large fireball. They were trapped for a short while in the cellar until the fire died down. They told firefighters that they’d seen a burning rag in the front yard Monday night but didn’t give it a thought until finding a bottle full of gas Tuesday morning. The fuse apparently fell out of the bottle before ignition during that attempt, firefighters said. The house sitters said they won’t stay at the place anymore.