The Valmeyer and Maeystown fire departments responded about 9 p.m. Monday to a fire in the basement of a duplex at 123 East Hunters Ridge in Valmeyer.
Heavy smoke was seen showing from the structure upon the arrival of a Valmeyer police officer to the scene.
The occupants of both units of the duplex were able to safely exit the structure. No injuries were reported in the incident.
Ameren was also requested and has dispatched a crew to the scene.