Several injured people have been transported to hospitals to be treated for chemical burns.

A chemical tank has imploded at a Nippon Dynawave Packaging facility in the US state of Washington, killing several people and critically injuring others, authorities said.

Emergency responders on Tuesday remained at the site in the city of Longview in Cowlitz County, about 70km (45 miles) north of Portland, Oregon, the Longview Fire Department said in a joint written statement with Nippon and the Cowlitz County Sheriff’s Department.

Multiple patients who suffered from chemical burns and other injuries were transported to nearby hospitals. Authorities said the implosion posed “no immediate threat to the surrounding community”.

The statement said that officials “can confirm fatalities related to the incident” along with “multiple critical injuries”, but did not provide figures.

At least nine workers and one firefighter were taken to hospitals from the site, said Scott Goldstein, the Cowlitz 2 Fire and Rescue chief who was among those who responded. The number of deaths was “undetermined”, he said at a news conference.

PeaceHealth St John Medical Center in Longview told ABC News it had seen nine patients related to the incident, including one who had died. Six of the patients were in fair condition, and two other patients had been transferred to other facilities, the hospital told ABC.

The joint statement said that a tank containing “white liquor”, a chemical solution of sodium hydroxide and sodium sulfide used in the production of paper pulp, had ruptured at about 7:15am local time (14:15 GMT).

Goldstein said at the news conference that the 80,000-gallon (about 300,000-litre) tank was approximately 60 percent full.

In southern California, meanwhile, authorities have been monitoring an overheating industrial tank containing methyl methacrylate, a highly flammable chemical used in the production of plastics. The worst-case possibility of an explosion was ruled out on Monday at the GKN Aerospace facility in Garden Grove after a crack relieved some of the mounting pressure, officials said.

Orange County Fire Authority spokesman Greg Barta said in an update on Tuesday morning that the temperature in the tank was holding steady and that crews were working to ensure that people evacuated could get home as soon as possible.