The body of a seventh victim has been recovered from the site of a chemical tank implosion and rupture in Washington state, officials said Friday, as efforts to dilute contaminated water continue.

On Thursday, officials said six bodies were recovered.

Eleven people are presumed dead in the incident at the paper mill in Longview, but the remains of two are yet to be recovered.

Longview Fire Chief Brad Hannig said Thursday the remains recovered from the site are decontaminated before they are sent to the Cowlitz County Coroner’s Office for identification, he said.

Recovery efforts continued Friday.

Longview Fire Battalion Chief Matt Amos said Friday crews used vacuum trucks and hundreds of feet of hose to clean up chemical water mixtures and move further into the implosion scene.

“So currently, we’re working inside much closer proximity to where we’re finding the victims, which is helping our recovery of our responders and our turnaround time,” he said.

The tank that imploded at the Nippon Dynawave plant is designed to hold 900,000 gallons of a hazardous chemical known as white liquor, which is used in the paper-pulping process. It was about 60% full at the time, officials have said.

The implosion occurred around 7:15 a.m. Tuesday as workers were in a shift change, and the six new recovered bodies were found in a workers’ area, Matt Amos said Thursday.

“It was in an area they would congregate in the mornings, where they would assemble, find out their assignments,” he said.

The tank contained sodium hydroxide, sodium sulfide and disodium carbonate, officials have said.

Following the implosion, officials have been diluting the high-pH water in ditches that was contaminated with the large amount of chemicals that spilled, officials said.

“A large amount of volume” of material, as well as water used by firefighters, flushed into a ditch across the street from the plant, said Brooks Stanfield, the federal on-scene coordinator for the Environmental Protection Agency.

Those efforts have been fruitful.

“We have started to see market improvement in the pH levels in the ditch, the ditch system, most specifically in the ditch here, right above the well fields,” Stanfield said Friday.

The ditch sits atop an aquifer and a well field from which Longview gets its drinking water, he said.

“Longview’s water is safe. There is no cause for concerns,” city Public Works Director Chris Collins said Thursday. He said officials were able to divert contaminated water away from a wellhead area.

The aquifers that supply the city’s drinking water are 200 feet underground, and the city’s water treatment plant is designed to automatically shut off to prevent contamination, the city said.

On Wednesday, officials began a plan to pull fresh water from the Cowlitz River to the east and push the contaminated water farther west and away from the wellhead area, Stanfield said.

That fresh water will dilute the contaminated water and flush it west, and then pumps will pull it to the west and discharge it into the Columbia River, he said.

The water is being monitored to make sure its pH level is lowered to normal levels before it ends up in the river, he said. The latest measurements were below the threshold pH level of 9, he said.

Officials said the Columbia River is safe for fishing and recreational activities.

The ditch by the plant is connected to a dike system that runs through the city of Longview, which has a population of around 37,000, Stanfield said.

“We are monitoring those. There are still areas with elevated pH in the water there, and we are continuing to tell people to stay away and to stay out of those ditches and dikes,” he said.

The disaster is likely to be the deadliest industrial accident in modern state history, Gov. Bob Ferguson has said.