SUPERIOR, Wis.  — Husky Energy says it’s been given approval to rebuild its oil refinery in Superior, Wisconsin after an explosion and a series of fires last year injured 36 people and required much of the city to evacuate.

Husky, which does business as Superior Refining Company in Wisconsin, said it will start the $400 million plan immediately with the goal of resuming partial operations in 2021.

Wisconsin Public Radio reports that residents and tribal leaders expressed frustration over Husky’s plans to continue using the highly toxic chemical hydrogen fluoride as part of its refining process. The city’s evacuation was largely because of the presence of hydrogen fluoride, which can be hazardous to human health. The tank containing the chemical wasn’t damaged by the explosion, which was caused by a hole in a valve.