Fatalities confirmed after chemical tank ruptures at pulp and paper mill in Washington state

A chemical tank ruptured at a facility in Washington state, resulting in multiple critical injuries and an unknown number of fatalities, authorities said.

The "hazardous materials incident" was reported Tuesday morning at the Nippon Dynawave Packaging, a pulp and paper mill in Longview, 128 miles south of Seattle, fire authorities said.

A tank containing white liquor ruptured at approximately 7:15 a.m., according to a joint statement from local authorities and Nippon Dynawave Packaging.

Authorities initially referred to the incident as a chemical explosion and then an implosion, before referring to it as a rupture.

More on this developing story at ABCNews.