(CNN) - A massive blast that rocked parts of an Illinois town Friday night has resulted in three deaths, with one person still unaccounted for as of Sunday evening.
The explosion happened at AB Specialty Silicones in Waukegan, about 40 miles north of Chicago, police said. The company describes itself as a manufacturer of specialty silicone chemicals.
The "catastrophic explosion" hit around 9:30 p.m. Friday, said Cmdr. Joe Florip, a Waukegan police spokesman. The plant was open at the time of the explosion, he said, and nine people were in the building.
Waukegan Fire Marshal Steven Lenzi said everyone affected was an employee working at the time. Four were taken to area hospitals with moderate to serious injuries, and one later died from injuries, officials said. Two others were seen but requested no treatment.
Three people were unaccounted for.
One person was found dead at the scene Saturday, Lenzi said. Authorities weren't able to continue any further recovery efforts until they brought in equipment to dismantle the "heavy unsafe structural remains."
Search will resume for one person missing
A second body was located on Sunday in "a heavily damaged portion of the building," according to a statement from the Waukegan Fire Department. "Due to the complexities of removing the victim from the debris it took crews over two hours" to recover the body, the statement said.
The search for the one person still unaccounted for will resume at 9 a.m. local Monday, Lenzi said.
No cause for the explosion has been determined yet. The state fire marshal and the Occupational Safety and Health Administration (OSHA) will assist with an investigation, Lenzi said
Florip said he would "categorize this as a massive explosion."
"Many neighboring properties are going to have damage," he said.
Damage is estimated at more than $1 million, Lenzi said. The blast affected at least five other nearby buildings.
After the explosion, the Lake County Sheriff's Office said on Twitter it was aware of "a very loud explosion sound" and "ground shaking."
Authorities later said they had no concern about air quality or a need to shelter in place.
"The Illinois EPA assisted with air quality monitoring and water runoff monitoring and the Waukegan Fire Department was not made aware of any public health concerns from this incident," Lenzi said.
Lenzi recalled one "fire instance" at the plant over the past 10 years. The plant has been "very responsive" and was "safety cautious after the incident from the previous fire," he said. "We have had no instances as far as code violations or anything like that with the plant."
CNN's Jay Croft contributed to this report.
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