Husky Refinery Was Shutting Down For Maintenance Before Explosion

MINNEAPOLIS (WCCO) – Investigators with the U.S. Chemical Safety Board say the Husky Refinery in Superior, Wis. was preparing for a five-week shutdown before an explosion last week injured 16 people.

Investigators say the refinery was shutting down to prepare for a five-week maintenance turnaround when the explosion happened. The incident sent several workers to the hospital, and thousands of residents living near the refinery had to be evacuated.

CSB investigators got there the night of the incident, and are still working on what caused the explosion. The investigation is expected to take several weeks.

On Wednesday, the mayors of Duluth and Superior called on refinery owners to stop using a toxic chemical compound on site.

The refinery is one of 50 across the country that still use hydrogen fluoride to process high-octane gas. It's a highly-corrosive chemical that can produce toxic vapor clouds.

The tank containing hydrogen fluoride was not damaged by the explosion or fire and none of the chemical leaked, company officials said.