Four people were injured, including two Chicago Police officers, in a residential fire Thursday morning in the Chatham neighborhood on the South Side.

Firefighters and a warming bus responded at 5:12 a.m. to the three-story building in the 600 block of East 79th Street, according to Chicago Police.

About 6:10 a.m. the fire was upgraded from a still and box fire to a two alarm fire, the Chicago Fire Department said. The flames were being fought defensively with three hose lines.

Two officers and two other people were taken to hospitals, police said. The officers were treated and released, but conditions for the two other people were not immediately available.

Fire officials said one of the officers had suffered “minor smoke issues” and one of the building’s occupants was taken to Jackson Park Hospital to be treated for smoke inhalation.

The fire was struck out about 6:45 a.m., the fire department said. According to preliminary findings by the CFD Office of Fire Investigation, it was an accidental electrical fire that started on the building’s second floor.