EDMONDS — Investigators now believe two separate blasts made up the fiery explosion that injured five people on Thursday at an Edmonds-area water treatment plant.
All five men are expected to recover from their injuries, officials said Friday.
The explosion has been ruled an accident.
It was reported about 11 a.m. at a construction site at the Picnic Point Wastewater Treatment plant along Picnic Point Road.
Fire investigators believe a propane tank was being moved when a brass valve sheared off, according to a county news release.
About 300 gallons of propane were exposed, and a truck driver yelled for everyone to clear the area.
The propane ignited less than a minute later, shooting flames into nearby buildings and trees.
Investigators later in the day determined that the fire also likely ignited flammable vapors in a building that was being painted. All of the injured people were in the building at the time, said Leslie Hynes, a spokeswoman for Snohomish County Fire District 1.
Damage from the explosion and fires was estimated at $1 million.
The explosion was determined to be an accident by investigators with the Snohomish County Fire Marshal’s Office.
An L&I investigation is common after someone is seriously injured in a workplace.
At this point, “it appears that Apollo has been doing everything possible to prevent injuries and keep workers compensation costs down,” L&I spokeswoman Elaine Fischer said.
Rikki King: 425-339-3449; email@example.com.