Medics airlifted five victims to the Seattle hospital for treatment of burn injuries, two of whom were in critical condition.

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An explosion at the Priest Rapids Dam on the Columbia River on Thursday injured six public-utility workers. Five of the workers were airlifted to Harborview Medical Center in Seattle to be treated for burns.

The blast around 4:15 p.m. was due to an electrical malfunction and did not compromise the hydroelectric dam’s structure, according to officials.

The six Grant Public Utility District employees were treated for injuries that ranged in severity.

Two men, both in their 40s, were at Harborview in critical condition and intensive care Friday morning, according to hospital spokeswoman Susan Gregg. Three other men are in satisfactory condition at the hospital.

Officials said the blast caused some electrical power and cellphone outages. Kyle Foreman of the Grant County Sheriff’s Office, one of the agencies looking into the incident, said investigators found no connection between the explosion and terrorism or criminal activity.

Grant Public Utility District spokesman Thomas Stredwick said the size of the explosion and its damage were unknown.

The hydroelectric dam is about 24 miles south of Vantage, Kittitas County.

It’s one of two dams that Grant Public Utilities constructed on the Columbia River to provide power to residents. A huge crack in the other, the Wanapum Dam, posed a risk of failure and prompted the creation of an emergency-response plan last year.

Both dams were built more than a half-century ago and span between 8,600 and 10,100 feet.