UPDATE 5p – Thursday morning's fire was started by a candle, the state fire marshal's office told DPS spokesperson Steve McCausland.
The office has also determined that the fire was accidental.
Investigators spoke with former resident Joseph Smith, who ws moving his belongings out of the building Wednesday night. Smith told them that he and his famioly had lived for a short time on the third floor of the building and was in the process of moving out.
Due to the building's power being cut off Wednesday, Smith told investigators that he had been using candles Wednesday night to see inside.
Investigators said the fire started in a stairway between the second and third floors.
Smith told them he discovered the fire and called the fire department just after midnight on Thursday morning.
WINDHAM, Maine (NEWS CENTER) -- An old mill building once occupied by squatters and makeshift apartments went up in flames Thursday according to Windham Fire Officials.
The squatters were evicted prior to this early morning fire that started around midnight on Three Mallision Falls Rd., according to dispatch.
At this time, we do not know if any injuries have occurred in connection with the fire, but the road is closed.
Fire officials have contained the fire but are still on the scene.
We will continue to update this story.
This video was sent in by NEWS CENTER viewer Jennifer Rogers Wescott, it shows the building engulfed in flames.