Officials say juveniles were seen leaving an abandoned building in Waterville, about half an hour before a fire started there Thursday afternoon.It happened on Harris Street.Crews from three area communities responded to the blaze.Fire fighters could see smoke as they approached the building.They say the fire started in a staircase leading up to the second floor.That’s a stable part of the building, so fire fighters were able to act quickly to put it out before the heat and humidity of the day became too much of a problem. “We moved to make a quick attack. Knock down the inside body of the fire. However, the fire had extended into a section between the ceiling and the roof. It continues to smolder so we have to cut the roofing material off to make sure the fire is out. We don’t want to come back,” Said Waterville Fire Chief David LaFountain.Police have been monitoring the abandoned building recently after transients were spotted in the area.