Photo by Derek Redd Fire damage can be seen on the exterior of the Tunnel Ridge Prep Plant. The plant was damaged in a major fire Monday night.

It is not yet known when the Tunnel Ridge mine’s prep plant will resume operation after a major fire Monday night, but the mine’s general manager said mine production was not affected.

The cause of Monday’s fire remains under investigation, said Tunnel Ridge General Manager Eric Anderson in an emailed statement. Damage to the prep plant, which separates the rock from the coal, was still being assessed.

A fire began inside the top two floors of the prep building at around 7:30 p.m. By 8 p.m., dozens of fire trucks and tanker task forces from Ohio, Brooke and Belmont counties were on the scene fighting the blaze. The fire was under control by around 11:15 p.m.

The plant was idle at the time, Anderson said, and only maintenance work was happening. All employees evacuated the plant safely and no injuries were reported. Federal and state officials have been notified.

Anderson said the mine continues to load and ship coal from inventory and it will continue to produce and store raw coal until the prep plant is repaired.