Firefighters say an apartment fire in Waterville was an accident, started by an electrical problem. Crews were called to a four-unit building on Western Avenue Tuesday afternoon. Lieutenant John Gromek says the fire started in the third apartment. He says a number of electrical items were plugged into an extension cord but there’s too much damage to figure out which one sparked the fire. It caused extensive damage to that apartment and the one below it. Everyone managed to make it out of the building safely. Firefighters were also able to locate two pet cats and two pet rats.