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Lakes Leisure chief executive Ruth Stokes says a young girl was showering inside the pool facility at the time.
"There was a massive white flash, the building went black, the girl screamed. One of our staff members was close at hand and raced over to see her," Ms Stokes told Newstalk ZB.
"The little girl's feeling was that she had been shocked."
Ms Stokes said the girl did not suffer any injuries and did not require medical attention.
The facility will be closed temporarily, and electricians are looking through the building.
Weather conditions also closed the outdoor Arrowtown Pool this afternoon.