Two fatalities had been confirmed after ​the tank containing “white liquor” — a chemical ​solution of sodium hydroxide and sodium sulfide ⁠used in making paper pulp — imploded ​at a Nippon Dynawave Packaging facility on Tuesday.

The ​search for the missing carried on through the week as recovery crews worked through debris in indoor ​areas and flew drones over the perimeter ​of the site, said Cowlitz 2 Fire & Rescue’s deputy ‌chief, ⁠Kurt Stitch.

The ruptured tank contained about 900,000 gallons (3.4 million litres) of white liquor, and tests confirmed that contamination entered the nearby ​Columbia River, officials ​have ⁠said, although no “negative health impacts” had been detected on air quality ​or the city of Longview’s drinking ​water.

Nippon ⁠Paper Industries, Japan’s second-biggest paper manufacturer by sales, acquired the Longview plant from Seattle-based timber ⁠company ​Weyerhaeuser for $225 million and established ​the wholly owned subsidiary Nippon Dynawave Packaging in 2016.