Two of the generators at the Ice Harbor Dam on the Snake River near Burbank were operating Friday and work was under way to start a third.
Small fires broke out inside two cabinets holding electrical components for two of the generators Friday.
Three of the dam's six generators were producing power then and were shut down. The other three were undergoing maintenance.
Friday, one of the shutdown generators began operating along with a second generator that had been undergoing maintenance. Crews had worked all night toward getting another of the generators that had been undergoing maintenance into service.
The cause of the fires remains under investigation.