At least one person was killed and nine others remain missing after a chemical tank imploded inside a pulp and paper mill in southwestern Washington on Tuesday, according to local authorities and company officials.

The incident occurred around 7.15am local time at a facility operated by Nippon Dynawave Packaging. Emergency responders described the site as a “mass casualty scene.”

Mike Gorsuch, battalion chief with the Longview fire department, said victims were decontaminated before being transported to hospitals in Longview and Vancouver. Around 40 firefighters, paramedics and a regional hazardous materials team responded to the emergency.

Recovery operations continued for several hours after the implosion. Authorities said the identities of the victims would not be released until family members had been notified.

In a joint statement, the company and law enforcement officials said the tank rupture caused multiple fatalities and serious injuries, including burn and inhalation cases. Officials added there was no immediate threat to the public.

The facility includes a pulp and paper mill and a liquid packaging plant that manufactures materials used in tissues, printing paper, cartons, cups and plates. According to the Washington State Department of Ecology, the site employs around 1,000 workers.