Deaths and injuries have been confirmed following the implosion of a chemical tank at a pulp and paper mill in southern Washington state on Tuesday, local authorities and company officials said. 

In a joint statement, Nippon Dynawave Packaging Co. and local law enforcement said the tank's rupture caused "multiple critical injuries" as well as fatalities, but specific numbers were not given. There are also some individuals who are unaccounted for, officials said at a news conference.

The explosion occurred in Longview, a city located along the southern Washington border with Oregon. 

"The scene remains in the recovery phase as emergency responders continue operations," the Longview Fire Department said in a statement on social media. "No identifying information regarding injured or deceased individuals will be released at this time pending notification of family members."

Authorities said there was no immediate threat to the public.

A spokesperson for PeaceHealth St. John Medical Center in Longview confirmed to CBS News that the hospital received nine patients from the incident, one of whom was deceased. An unknown number of patients were also being treated at the Legacy Oregon Burn Center in Portland, Oregon, Legacy Health confirmed to CBS News in a statement.

Among those injured was a responding firefighter. Authorities said some victims had suffered burns or inhalation injuries, and that the severity of the injuries ranged from minor to critical.

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

The fire department said a tank containing white liquor ruptured. White liquor is a chemical commonly used in paper and pulp processing which consists of sodium hydroxide and sodium sulfide.

Cowlitz Fire and Rescue Chief Scott Goldstein said the 80,000-gallon tank that imploded was about 60% full. It was too early to determine the cause of the implosion, Goldstein said.

"We're dealing with life safety concerns and incident stabilization at this point," he said.

The Nippon Dynawave Packaging Co. facility is a pulp and paper mill and liquid packaging plant that makes material for tissues, printing paper, cups, plates, cartons and other goods. It employs about 1,000 people, according to the Washington State Department of Ecology.

About 40 firefighters and paramedics had responded, along with a regional hazmat team, Gorsuch said. The incident was reported at 7:19 a.m. local time.

Nippon Dynawave did not immediately respond to a request for comment.

Meanwhile, thousands of Southern California residents remained evacuated on Tuesday due to a damaged chemical tank at an aerospace plant.