WASHINGTON: The death toll from a chemical tank rupture at a paper manufacturing facility in the US state of Washington has risen to 11 after rescue crews recovered the bodies of all nine workers who had been missing since the incident, authorities said on Saturday.

Two fatalities were confirmed earlier after a large storage tank containing “white liquor” exploded at the Nippon Dynawave Packaging plant in Longview on Tuesday. The chemical, a mixture of sodium hydroxide and sodium sulfide, is commonly used in paper pulp production.

Search and recovery operations continued for several days as emergency teams sifted through debris inside the facility and used drones to scan the surrounding area. Officials from Cowlitz 2 Fire & Rescue said crews worked methodically until all missing individuals were accounted for.

Authorities said the ruptured tank held around 900,000 gallons (3.4 million litres) of white liquor. Testing confirmed that some contamination reached the nearby Columbia River. However, officials stated that no harmful impacts had been detected in air quality or in the drinking water supply of the city of Longview.

Investigations into the cause of the tank failure are ongoing.

The facility is operated by Nippon Dynawave Packaging, a subsidiary of Japan’s Nippon Paper Industries, which acquired the Longview plant from Weyerhaeuser in 2016 in a $225 million deal.