In the minigames when you finish the night, there are drops that come down from the ceiling. I feel like this is some sort of malfunctioning emergency water system to put out fires, and the Phone Dude warns us of fire possibly because it's happened before. The fire itself is probably in an inaccessible room, such as the ones with tape that you cannot enter. Possibly, the fire stopped but the sprinkler system is still malfunctioning, therefore causing drops to fall. Or it could just be leaks in the ceiling from the storm.