WARREN TOWNSHIP - Firefighters from four departments battled a fire at the former Hammer Jack's bar and restaurant for nearly five hours early this morning. According to Warren Township officials, the blaze was reported about 1:30 a.m. today at the 3405 Mahoning Ave. building. Firefighters closed off Mahoning Avenue at times while battling the blaze, and departments from Champion, Warren and Howland assisted. A cause hasnát been identified, said fire officials, who were investigating this afternoon.