Firefighters called on neighboring communities to deliver tankers full of water as they fought a losing battle against heavy flames Friday at a multimillion-dollar mansion in Concord. The fire at 240 Fairhaven Hill Road burned a 6,500-square-foot home that was built in 1899, according to records. The five-bedroom, five-bathroom mansion is valued at approximately $2.9 million. Historical records show the home was designed by Boston architect H.D. Hale for Charles Francis Adams III, a secretary of the US Navy and descendant of President John Quincy Adams. It was one of the first two large country estates not associated with farming in the town. Concord Assistant Chief Walter Latta said the current homeowners were away when the fire started. No injuries were reported. "It's a large house, and as you can tell, it's in a remote area," Latta said. "We're trying our hardest. The crews are doing a great job."Firefighters struck at least three alarms, bringing in help and equipment from Acton, Boxborough, Carlisle, Lexington and Stow. "The fire was in the rear of the house and it just ran the walls," Latta said. "(An) old school building, balloon frame, and so the fire started extending to the second floor and then the third floor."Sky5 arrived over the scene around 10:50 a.m. and saw flames bursting from the roof. Multiple fire department units were there and firefighters were seen in the front door of the home, but there was little activity with fire hoses until approximately 11:10 a.m. Latta explained the property is elevated and firefighters had quickly used all the water available in a nearby cistern. To supplement the water supply, Latta said Concord relied on tankers from neighboring fire departments. The tankers hauled water to a yellow portable holding tank. From there, water was being pumped into the hoses for firefighters to use against the flames. Between the tankers and the cistern, firefighters had used approximately 10,000 gallons of water by 11:50 a.m., Latta estimated. "We're doing everything we can," Latta said. "I know this is the holiday season and this is devastating, but the most important thing is nobody got injured."As helicopters circled overhead, the flames continued to spread throughout the mansion until it seemed to reach every corner of the structure. The portico collapsed and large sections of the roof caved in. Flames were still raging at 1 p.m., having spread to every corner of the building. By 2 p.m., the once stately mansion was reduced to a smoldering shell as firefighters continued to douse hot spots.