Officials with the Ottumwa Fire Department informed KTVO Thursday evening that the fire started in the living room.
The investigation will continue Friday.
The Ottumwa Fire Department responded to a house fire on Thursday afternoon near Fellows and Main Street on Ottumwa's east side.
Ottumwa Fire Chief Tony Miller told KTVO on-scene that the second floor of the house is no longer standing.
At this time there have been no reports of any injuries.
The American Red Cross is assisting two adults and one teenager who lived inside the home.
KTVO will update this developing story as additional details become available.