Squatters are believed to be responsible for a fire early Friday morning at a vacant building in Red Bluff. A little after 3AM, Red Bluff Firefighters got a report of a house fire with a person possibly trapped inside. When they arrived at 237 Main Street, they found heavy smoke coming from an old residence that had been converted into a business, but was not currently being used by the owner. Someone was using it, though. When the firefighters made a search of the interior, they didn't find any people, but there was evidence that squatters had been living there. The fire was burning in the floor with extension into a wall. Main Street was closed for two hours while the fire was extinguished. There was no gas or electric service to the building. The exact cause of the fire is undetermined, but investigators are certain it was human-caused.