A fire that caused an estimated $125,000 damage to a Mount Savage home Friday evening remains under investigation, the Office of the Maryland State Fire Marshal said.  The blaze at 13009 Irving Street started about 5:30 p.m. Investigators said residents escaped without injury after a passerby alerted them to a fire under a deck.  More than 50 firefighters battled the fire at the home owned by Lorri Ann Melon. One firefighter was treated for possible heat exhaustion.