A security guard who police once made a mascot has been charged with setting a spectacular waterfront blaze that caused about $10 million in damage, authorities said. Claude Douglas Melcher, 22, also was being questioned in a $20 million, nine-alarm fire two years ago that burned for several days and displaced hundreds of residents, police said. ``There are a lot of other fires we intend to question him about,'' said Sgt. Richard J. Ellwood. Melcher, who according to today's editions of The Sun often carried a plastic gun in a police holster and a police-fire radio scanner, was held on $100,000 bond Wednesday night after his arrest a day earlier. According to the newspaper, police and firefighters said he had visited station houses for 12 years and often ran errands for officers, who made him a mascot and outfitted him with shirts, trousers, even a night stick. A firefighter quoted by The Sun without identification recalled Melcher frequently arriving on the scene of fires before he got there. ``He would beat us there, and then he would want to help with the firehose or something,'' the firefighter said. Five firefighters suffered minor injuries battling the $10 million, seven-alarm blaze in the city's Fells Point section April 13. It began behind a building at Autoline Lubricants Inc., then spread to a shack at Allied Chemical Corp. Melcher returned to a fire station after the fire and talked with firefighters about it, fire officials said. The $20 million blaze destroyed a warehouse, three houses and damaged up to 120 homes and businesses on Nov. 4, 1986. Melcher was arrested after investigators questioned him about an Oct. 12 fire that caused $800,000 in damage at a building under construction at the Francis Scott Key Medical Center, where he is a security guard.