Four people in an apartment building on West Pearl Street were sickened Friday night when a furnace malfunctioned and flooded the building with carbon monoxide.

Capt. Tom Fair of the Butler Fire Department said Saturday morning that firefighters arrived at the two-story building at 120 W. Pearl St. to discover high readings of the hazardous gas.

The building has four apartments.

Fair said a boiler for one of the upstairs apartments had malfunctioned, causing the gas to leak into the building.

Fair said four people were living in three of the apartments and all complained of dizziness and nausea but were not taken to the hospital.

Firefighters cut off power to the furnace, which runs on natural gas, and cleared the building of carbon monoxide, Fair said.

Peoples TWP was contacted to inspect the furnace, Fair said.