LONGVIEW, Wash. (AP) — A massive chemical tank holding nearly a million gallons of a corrosive liquid imploded and collapsed Tuesday at a Washington paper mill, killing at least one worker and leaving nine others unaccounted for, authorities said.

Nine other people were injured in the spill, some severely. Emergency responders were still working on recovery efforts at Nippon Dynawave Packaging Co. in Longview, but hours after the implosion, some liquid remained in the collapsed tank, complicating efforts to reach victims, the Longview Fire Department said Tuesday evening.

“The tank remains unstable, creating hazardous conditions for emergency personnel,” the fire department said in a written statement. “Responders are continuing efforts to structurally reinforce and stabilize the site before additional recovery operations can safely proceed.”

Among those injured was a responding firefighter. Some victims had suffered burns or inhalation injuries, and the severity of the injuries ranged from minor to critical, authorities said. There was no immediate threat to the public, they said.

Some people waited at the company’s visitor entrance on Tuesday, seeking information about loved ones who worked at the facility. They declined to comment to an Associated Press reporter. At a nearby union hall that was serving as a family assistance center, three women shared a tearful embrace before heading inside. Others arriving at and leaving the building were also seen in tears.

The Nippon Dynawave Packaging Co. facility is a pulp and paper mill and liquid packaging plant along the Columbia River in Longview, a city of about 38,000 that has had a relationship with the paper and lumber industries since its founding by a Kansas City timber baron in the 1920s.

The facility, which employs about 1,000 people and dates to 1953, makes material for tissues, printing paper, cups, plates, cartons and other goods. It is located in an industrial zone shared by other timber, paper and chemical businesses, and it remains central to the community.

“The people who are responders here have friends and relatives that work on site,” Cowlitz Fire and Rescue Chief Scott Goldstein noted. “It is something that is impactful, and we have support networks to support the workers as well as the emergency responders.”

Officials initially reported that the tank had a capacity of 80,000 gallons (303,000 liters), but later revised that number to say it was holding about 900,000 gallons (3.4 million liters) of a chemical brew known as “white liquor.” The liquid, which consists mainly of sodium hydroxide and sodium sulfide, is used with heat to break down wood to make kraft paper, a durable material used in packaging, shopping bags and other products.

It was too early to determine the cause of the implosion, Goldstein said.

In a written statement, U.S. Sen. Patty Murray of Washington called the implosion an “absolute tragedy.”

“My heart is with everyone who lost a loved one today — as well as the injured workers,” she said.

Mike Gorsuch, battalion chief with the fire department in Longview, Washington, described it as a “mass casualty scene.” He said first responders had decontaminated patients and taken them to hospitals in Longview and Vancouver, Washington.

About 40 firefighters and paramedics had responded, along with a regional hazmat team, Gorsuch said.

Following the tank’s rupture, the white liquor spilled into a drainage ditch, said Brittny Goodsell, a state Ecology Department spokesperson. The department sent a team to evaluate the impacts, Goodsell said.

Thousands of residents of Southern California remained evacuated Tuesday due to a damaged chemical tank at an aerospace plant.

Just over 40 people died between January 2021 and mid-October 2023 as a result of hazardous chemical incidents, according to a paper released by a network of environmental justice organizations in late 2023.

Nippon Dynawave, a subsidiary of Japan-based Nippon Paper Group, has been fined a total of $3,400 for three separate health and safety violations found by Washington Department of Labor and Industries inspectors since the start of 2021, according to the department’s online database.

In one inspection, the company was cited because face coverings were not worn by every employee when required. In another, the inspector determined that an employee was exposed to the risk of falling while working on a platform more than 4 feet (1.2 meters) off the ground without fall protection measures in place.

In the third incident, the department determined that equipment involved in a work-related accident — an amputated finger — was moved from its original position before the state’s investigation into the accident was complete.

Online records from the U.S. Department of Labor’s Occupational Safety and Health Administration show safety complaints were filed against Nippon Dynawave on March 4 and May 6, but both cases remained open and details about the nature of the complaints were not available online. OSHA officials did not immediately respond to a request for additional information.

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Boone reported from Boise, Idaho. Associated Press reporters Gene Johnson in Seattle and Christopher L. Keller in Albuquerque, New Mexico, contributed.

Claire Rush And Rebecca Boone, The Associated Press