The bodies of six missing employees have been recovered after a chemical tank ruptured at a paper mill in Longview, Washington, raising the confirmed death toll to eight.

Three workers remain unaccounted for as recovery efforts continue in what officials warn could be one of the state’s worst industrial disasters.

The explosion involved a tank of “white liquor,” a hazardous chemical used in paper production, which caused extensive damage and contamination concerns.

Emergency crews continue to carefully search the site under hazardous conditions while state and federal agencies investigate the cause, ABC News has reported.

Officials also confirmed some chemical contamination reached the nearby Columbia River, though local drinking water supplies remain safe.