BEAVERTON, Ore. -- Power has been restored for approximately 50,000 people in Washington County after a large transformer fire Saturday night.

Firefighters responded to an explosion at a Beaverton substation located at 1785 SW 158th Avenue and found a 50-foot transformer ablaze Saturday at 7:25 p.m.

As firefighters continued to arrive, a second explosion occurred. Officials described it as a “500 foot fireball over our heads.”

Concerned about a third explosion of a 20,000 gallon mineral oil tank, crews pulled back from the substation area.

Authorities then let the transformer burn over the course of several hours after they ruled the fire was contained and did not pose a hazard to surrounding homes and businesses.

The cause of the fire has yet to be determined.

PGE estimated 50,000 people in Beaverton, Aloha, Gaston and banks were without power.

All roads around the substation were closed for about four hours. Light rail stopped running in Washington county as a result of the fire.

At the time of the fire, crews and contractors were still mopping up problems from a major windstorm that swept through Oregon and knocked out power to 250,000 people.