The Columbia Falls Weyerhaeuser MDF plant was rocked by an explosion and fire about 7:50 a.m. Wednesday, Feb. 19. 

The explosion may have been caused by an electrical arc in the power distribution center, which runs both lines of the plant, Columbia Falls Fire Chief Karl Weeks said.

No one was injured in the blast, which blew walls out of the building and garage doors off their hinges.

The electrical surge at the time was so great that Flathead Electric Co-op noticed the power draw on the grid, Weeks said.

A man who was driving his children to school said he saw a fire ball rise 200 feet into the air at the time of the explosion.

Weeks said plant workers also saw a fire ball. He said the call came out at 7:51 a.m. and the first firefighters were on the scene 8 minutes later. He said firefighters battled active fire inside the building until 12:51 p.m. and were still on the scene hitting hot spots at 4 p.m.

Damage, including downtime of the mill, which is designed to run continuously is still under investigation by company officials, Betsy Earls public affairs manager with Weyerhaeuser said.

The ALERT helicopter circled the scene several times but did not land and Three Rivers ambulance was on standby at the initial stages of the fire.

Temperatures at the time were in the low teens

Bad Rock, Evergreen, Whitefish and Kalispell fire departments all responded with mutual aid.

The plant has an extensive fire suppression system but has caught fire in the past. MDF is made from sawdust particles, which can be highly flammable. The wood fibers are glued together under immense pressure from huge presses which makes the fiberboard.

The production lines were not damaged.

The plant has two lines and is capable of producing 265 million square feet of 3/4-inch MDF annually. The plant has about 200 employees.

Columbia Falls and other area fire departments were called back to the Weyerhaeuser MDF plant about 6:50 a.m. Friday.

The plant had a hot spot in a wall that company crews were unable to get out, explained Columbia Falls Fire Chief Karl Weeks. Crews at the plant have been putting out hot spots since the plant suffered an explosion on Wednesday, Weeks noted.

Firefighters were off the scene by 8 a.m.

"We will resume normal operations when it is safe to do so," Weyerhaeuser spokesman Matt Peterson said. "We appreciate the ongoing support of local first responders and firefighters and are grateful for their assistance at the scene."