O’Fallon firefighters were called to a report of a fire Tuesday morning at the Drury Inn in O’Fallon, but they found no fire.
Fire officials said a malfunctioning heating system apparently set off smoke detectors.
Occupants were evacuated, but quickly allowed to return to their rooms.
Emergency radio transmissions indicated there was smoke seen at the hotel.
Firefighters were called shortly after 9 a.m.