Multiple people were killed after an implosion at a packaging facility and paper mill in Washington state on Tuesday morning, fire authorities in the city of Longview said, after a tank of white liquor ruptured causing “chemical burns and other injuries.”

A tank of white liquor imploded at the Nippon Dynawave Packaging Company in southern Washington state on Tuesday.

The chemical leak occurred at the Nippon Dynawave Packaging Company—a kraft pulp and paper mill and liquid packaging plant that employs hundreds of workers, according to Washington’s Department of Ecology.

The implosion caused “multiple critical injuries” and an unknown number of fatalities, the Longview Fire Department said at a press conference on Tuesday.

Several people remained unaccounted for, a spokesperson for the Fire Department said at the press conference, but further details about the victims have not been released.