The cause of a fire Monday, Jan. 29, that filled Fisher Engineering's manufacturing plant with smoke remains under investigation.

This was the third fire at the snowplow maker in three months.

Rockland was joined in its efforts at the scene by crews and equipment from Thomaston, Camden, Rockport, Owls Head and Northeast Mobile Health ambulance service. The additional towns were called in to assist when Rockland firefighters entered the building and were met by heavy smoke.

This fire had spread to the roof of the sprawling manufacturing plant at the end of Gordon Drive in the Industrial Park.

The fire was reported at 7:10 a.m. The initial report from the fire department was that the fire was located above the sprinkler system. Firefighters were being put on the roof of the building via ladder trucks.

The plant was evacuated. Central Maine Power arrived at about 8 a.m. to shut off the electricity.

Firefighters came down from the roof shortly after 8:30 a.m., but remained on scene for a few more hours.

The Maine Fire Marshal was called in to help find the cause.

This is the third recent fire at the plant. On Jan. 19, a fire that started in an air exchange system filled the plant's interior with thick smoke. On Nov. 1, a small fire was quickly extinguished. There were no injuries in either of those fires.