Many employees have reported problems breathing after thick smoke filled the building at 8:30 a.m. Tuesday at Arens Control Company.
Officials say a piece of machinery exploded inside the plant.
Emergency responders were still on the scene on Kennicott Road, unable to go inside because of the amount of smoke in the building almost three hours later.
A few minutes ago the chief of the fire department in Arlington Heights said they found one person had died at the site of the machine that exploded. They had to transport 10 people to the hospital with some form of respiratory distress. They don't expect any of those injuries are severe.
Seven of those people were employees, but three were police officers who were the first ones on the scene and tried to go in to help.
Authorities evacuated the building, which had an estimated 50 people inside.
Arens is a company that produces technology of all sorts. They said machine testing was going on when the explosion happened, but emergency officials are still trying to determine the exact cause.
"There was some form of explosion, but right now we really can't get in there to assess the scene because again, the building is still full of smoke. We are going to have to wait until the air quality improves before we can go in to actually determine what happened," said Chief Glenn Erickson, Arlington Heights Fire Dept.
There were initial reports that some sort of chemical had been involved in the explosion, and it was, but it did not escape from the building. There was never any danger to anybody in the community.
The police department said they are going to hand the scene over to the Occupational Safety and Health Association so they can determine if proper procedures were being followed at the time of the explosion.
Representatives from Arens have yet to comment. All employees have been sent home for the day.