Crews on Friday recovered the remains of one more victim of a massive chemical tank rupture at a paper mill in Washington state, bringing the death toll to nine people and leaving two workers still unaccounted for.

Among the 11 workers presumed killed in the disaster were two brothers who worked there together, a trivia champ and an electrician who would help his farmer neighbors cut hay.

A tank containing more than 500,000 gallons of a mixture used to break down wood for making paper collapsed on Tuesday morning at the Nippon Dynawave Packaging Company in Longview, a city along the Columbia River.

The collapse expelled a flood of caustic chemicals powerful enough to overturn pickup trucks and damage buildings at the site. The liquid, called white liquor, causes severe burns on contact and lung damage if vapors are inhaled.

The recovery of victims has been slow and methodical, complicated by the dangers posed by the remaining chemicals and other industrial hazards, said Matt Amos, Longview fire battalion chief.

Six bodies were found on Thursday.

Crews were steering clear of a zone closest to the tank and they have been working with engineers to determine which damaged buildings near it are safe to enter.

As they collect the remains, crews must decontaminate them before turning them over to the coroner’s office for identification. The searchers also must decontaminate themselves.

The tragedy is one of the deadliest US workplace accidents in recent decades and its cause is under investigation.

Authorities have not released the names of those who were killed, but friends and relatives had begun confirming their names and posting online fundraisers to support their families.

Among those presumed dead were brothers Tyler and Brad Covington, who worked together at the plant. An online effort to support Tyler Covington’s family noted he “leaves behind his wife and their three beautiful children, who are now trying to navigate a future without the man who was their rock, protector, and greatest source of love and support”.

Gilbert Bernal, a grandfather who was an electrician at the plant, was the first confirmed death, his friend Todd Cornwell said.

“He was one of the most genuinely good people that you’ve ever met. He would give you the shirt off his back if you needed it,” Cornwell said.

John Forsberg, who also died in the collapse, was witty, kind and “wicked smart,” said friend Kole Musgrove, who hosts a trivia night at Ashtown Brewing in Longview, where Forsberg regularly competed.

The brewery is renaming its trivia trophy the Forsberg Cup to honor him.

“It seemed like there was never a fact he didn’t know,” Musgrove said. “He was also a tremendous sport – he was always the first to cheer for another team when they won.”

A GoFundMe post sought donations for Forsberg’s two children.

CJ Doran, 26, was “the spiritual leader of their family, the joy of their home, and the family provider,” according to a GoFundMe post verified by the crowdfunding site.

Other victims included Jared Ammons, who had two children and another on the way, and Braydon Finkas, an electrician at the plant, who, along with his longtime partner, Kaitlyn Kincaid, hosted exchange students and others in need, according to their friend Rex Czuba.

Finkas moved to Cathlamet about four years ago to build a house and start a farm, Czuba said. He always was willing to help other farmers cut hay or load equipment, or buy a beer for a new face in their small town, he said.

“He really jumped in and became a part of the community so quickly,” Czuba said.

The tank failure also injured eight people, including a firefighter. Some suffered burns or inhalation injuries, authorities said.

The mill’s Japanese parent company, Nippon Paper Group, said in an updated statement on Friday it was offering its “heartfelt sympathies to the bereaved families”.