Xcel Energy shut down its 538-MW Black Dog Power Plant in Burnsville, Minn., on Tuesday after an explosion rocked the coal- and gas–fired plant, causing visible damage to the exterior of the building. No personnel were harmed, but three firefighters responding to a smoldering fire in a coal hopper received minor injuries, police said.

Burnsville police said that the explosion occurred at 8:25 a.m. in the coal hopper during fire suppression, nearly 45 minutes after the fire department responded to a smoldering fire in the hopper. At 2 p.m. on Tuesday, firefighters were still battling the fire in the hopper and an additional blaze on the roof directly above it. Fire officials remained on the scene until late afternoon.

Damage to the plant included a number of blown out windows and pieces of wall (video). The utility vacated the plant and shut it down for safety reasons. Xcel Energy spokesperson Thomas Hoen told POWERnews that the plant would remain shut in the near future, though the incident was not expected to interrupt power service to customers.

“We have begun the process of assessing the damage and hope to have that assessment completed by the end of the week. Once we know what level of damage we have, we will be able to put a restoration plan together,” he said. “A cause to the incident is still being investigated as well.”

The first of the plant’s five units came online in 1987, according to Xcel Energy. A coal-fired unit was recently replaced with a natural gas unit. The plant continues to burn mainly low-sulfur western coal.

Sources: Burnsville Police, Xcel Energy, POWERnews