Gazette photo by Andrew Wallmeyer About 40 firefighters from the Bayport, Stillwater and Lower St. Croix fire departments responded to a call from the Xcel Energy's Allen S. King plant shortly before 6:30 p.m. Tuesday night.

OAK PARK HEIGHTS - A fire spread through the coal-handling system at Xcel Energy's Allen S. King plant shortly after 6 p.m. Tuesday night, causing an explosion strong enough to blow through a corrugated steel wall. No one was injured in the incident.

About 40 firefighters from the Bayport, Stillwater and Lower St. Croix fire departments responded to the call, which Bayport firefighters on the scene said they received at 6:26 p.m.

As of 10:30 p.m., fire officials and Xcel Energy representatives said the exact cause of the fire was still unclear.

Bayport Fire Chief Mike Bell said the explosion occurred after plant workers noticed abnormally high carbon monoxide levels in part of the coal-handling system and went to investigate. They opened a door in the seventh-floor coal-storage bunker and put out a small fire there. At some point, a sprinkler system went off, the force of which Bell said likely kicked coal dust into the air that ignited and caused the explosion.

"Eventually, the sprinkler system would put the dust down, but the initial blast of the water actually kicks dust up," he said. "Any time you hit coal or sawdust with water, that first blast aerates it. So a lot of times you get an explosion of the first blast. It looks like that's what happened here.

"It blew a couple of access panels off of the conveyor system, and then there was a secondary fire that the corrugated steel wall out, so it was a pretty significant explosion," Bell continued. "But there was nobody injured. They all made it out okay and everybody was accounted for."

The incident prompted the plant to begin its shutdown procedure, which takes about 13 hours, Bell said at about 10 p.m. In the meantime, plant workers and firefighters were checking to make sure no other fires were burning in the facility's coal-handling system.

At 10:30 p.m., Xcel Energy spokesman Tom Hoen said he couldn't confirm the details of the incident, and he wasn't sure what caused the fire or what long-term effects it would have on the Allen S. King plant, which runs 24 hours a day and produces about 575 megawatts, enough to power nearly 600,000 homes.

"I can tell you no injuries were reported, which is the most important thing, but don't know anything about the nuances of the fire itself, at this point," Hoen said. "I'm sure we'll be able to tell you a lot more tomorrow, after the firefighters have finished up their work and we've had a chance to take a closer look at the situation."