Fire service subsequently rescued seven people from the scene in Charail after the incident on Friday.
Lima Khanam, an officer at the fire service control room, said the building tilted to one side around 8:30 am and fell into the swamp.
Six units of the fire service subsequently rushed to the spot and started the rescue operation. Among the seven who were rescued, two women have been sent to hospital while the others received first aid.
Lima said a tin-roofed third floor had been added to the two-storey structure near the Purbacharail playground.
However, it was not immediately clear whether the construction work had been carried out in accordance with the law and with the approval of the authorities.
“The owner of the house says there’s no-one else left in the building. We have not received any information about any fatalities yet. Our personnel are searching the building to see if anyone else is left trapped inside,” said Lima.