Before officers arrived, someone used a fire extinguisher inside the apartment building.
Police found a large group of people and a knife.
Four officers were exposed to chemicals from the fire extinguisher.
They were taken to a hospital for treatment.
They were later released, and returned to work.
The apartment complex was evacuated for the night so crews could clean up.
The Red Cross assisted residents after the evacuation.
Six people could face charges because of the disturbance.