Three years ago, an explosion rocked Wisconsin's only oil refinery in Superior, injuring three dozen people and causing a temporary evacuation of city residents. But investigators with the U.S. Chemical Safety and Hazard Investigation Board have yet to release a final report on their investigation into the blast.

The Duluth News Tribune first reported that former employees and government auditors found that the agency has faced a shortage of staffing and unfilled board positions that have contributed to a backlog of investigations.

The Chemical Safety Board’s website currently shows 20 active investigations. They include reviews of the April 2018 explosion at the Husky refinery in Superior and the May 2017 explosion at the Didion Milling Co., in Cambria. The two events are among the four oldest incidents currently under investigation.

Superior Mayor Jim Paine said the delay in the final report on the explosion is "disappointing."

"The best opportunity for safety improvements is during reconstruction — redesign," said Paine. "If this report comes out with a significant recommendation about a major change in operations at the refinery, that's going to be much harder to implement after reconstruction is done."

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