Firefighters were able to extinguish the fire rapidly, said Montgomery County Fire Battalion Chief Dan Ogren. (Courtesy Montgomery County Fire and Rescue Service) WASHINGTON — Investigators are still working to find what caused a house fire that killed a man in Bethesda earlier this month. But the investigation is far from routine after investigators found tunnels, chemicals and wiring in the basement. “The conditions in the basement became more and more unusual as the investigation went on,” Montgomery County Fire Chief Dan Ogren said Tuesday in describing the site of the house fire on Danbury Road. Firefighters responded at around...