COULEE DAM — The U.S. Bureau of Reclamation will launch an investigation into a fire and explosion at Grand Coulee Dam on Saturday that has apparently damaged one of four powerhouses.

No one was injured in the explosion, which was reported at 9 a.m., said Lynne Brougher, Reclamation spokeswoman.

The explosion and fire apparently occurred on a large power line encased in a “buss” — like a conduit — that connected one of the powerhouse’s nine generators to an external transformer.

The generator itself doesn’t appear to be damaged, Brougher said, but the entire powerhouse was taken offline as a precaution, until investigators can get inside for a look.

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The powerhouse was generating at the time of the explosion, she said.

The dam has 33 generators, so no decline in power generation or outages resulted from the explosion, she said.

The powerhouse, which is along the Columbia River’s east side, has been closed until air-quality tests for the presence of lead and asbestos come back, Brougher said. It is not one of the powerhouses open to the public during the tour season, she said.

Firefighters from reclamation’s own on-site fire department responded, along with crews from the cities of Grand Coulee and Coulee Dam, she said.

The damage is not visible from the Visitor Center, she said, but visitors at the time of the incident could see fire crews responding.

It may be weeks before investigators can say what caused the fire, she said.