Authorities have ruled as accidental a Thursday morning fire that left a Cambridge townhome ruins. The Maryland State Fire Marshal's Office said the two-alarm blaze was reported shortly after 11 a.m. at the two story dwelling located at 210 Wood Duck Drive. Both the home's smoke and fire alarms were present and activated, according to investigators. It took 54 firefighters from the Rescue (Cambridge) Fire Company and assisting companies approximately an hour and a half to get the fire under control. An estimated $100,000 in damage was done to the structure with another $40,000 in damage to its contents. There were no reported injuries. Deputy state fire marshals determined the fire started in an attached garage and was caused by an unspecified electrical event.