Washington Gov. Bob Ferguson expressed sympathy for the victims, their families and first responders. He also said responders from the state Ecology Department had been sent to the scene.
Officials said there was no immediate threat to the surrounding community but urged people to avoid the area.
White liquor is used in papermaking and contains chemicals such as sodium hydroxide, sodium sulphide, and disodium carbonate.
Officials first gave a smaller estimate of the tank’s size but later said it held about 900,000 gallons of the chemical mixture.
Nippon Dynawave Packaging, a subsidiary of Japan-based Nippon Paper Group, operates the Longview facility, which produces packaging board and pulp products used in items such as milk cartons, food containers, tissues, printing paper, cups and plates.
The plant employs about 1,000 people and is located in an industrial area shared by other timber, paper and chemical businesses.
State records show the company has been fined for three health and safety violations since 2021. Two more safety complaints were filed earlier this year, but state officials said they were not related to the tank that ruptured.
