The U.S. Chemical Safety Board has released the results of their investigation into the Huskey Refinery fire in Superior.

They blame internal wear on a valve for the explosion and the resulting fire hours later. The explosion injured 36 people and was responsible for the evacuation of nearly all of Superior and some surrounding areas on April 26th.

The original explosion sent debris flying 200 feet which punctured an above-ground tank that dumped 15,000 barrels of hot asphalt, causing the huge fire that burned into the evening.

The CSB put together the following video that breaks down some of the technical details of the explosion and fire.