It happened shortly before 10 p.m. Friday at the AB Specialty Silicones in Waukegan, Illinois.
Waukegan Fire Chief George Bridges Jr. said that the three people who went missing in the ruble alerted their co-workers to the problem just before the explosion occurred, saving several lives.
On Saturday afternoon, crews suspended their search for the two missing workers because of concerns about the stability of the structure.
CNN reported that the fire had been extinguished, and hazardous materials technicians and other teams were on the scene and searching for three employees who remained unaccounted for. Fire officials recovered one body Saturday.
This was after one body was found at the explosion site, with two more believed to be missing.
An investigation is now underway to determine the cause of the explosion. Nine employees were inside the plant at the time.More news: Stock futures plummet as Trump threatens to hike tariffs on China
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Authorities later said they do not believe there is cause for concern about air quality or a need to shelter in place. Two others were seen but requested no treatment.
Two others at the plant, a 30,000-square-foot facility that operates 24 hours a day, were able to walk away unharmed. The blast affected at least five other buildings nearby.
AB Speciality Silicones is a manufacturing and distribution company that specializes in producing raw silicone products. Officials from the Occupational Safety and Health Administration will investigate.
The Lake County Sheriff's Office told residents it was aware of the "very loud explosion sound" and "ground shaking", but deferred questions to the Waukegan Fire Department.
Lenzi says it's "not likely" anyone survived the Friday night explosion at AB Specialty Silicones in the community 50 miles north of Chicago.
Lenzi says more than 100 firefighters from at least 30 departments responded to the scene.
"We have spent the day trying our best to support all of the members of our AB family as Wednesday attempt to process this awful loss together", he said.