"[The] people were treated for injuries [burn wounds] at the Wilhelm Stahl Hospital," said police spokesperson Stefanie Smith.
It was believed an explosion at Rolfe Laboratories sparked a fire that resulted in the evacuation of the building.
She said rescuers were searching a part of the building that was badly damaged for people who might be trapped.
"A head-count is still in process by the company to determine who was on duty at the time of the explosion and to determine the casualties."
Police were investigating a case of arson. The estimated damage had not yet been determined.