Most of the nine family members including the house owner were found in an unconscious state in their flat and their valuables stolen at a building in Delpara area of Fatullah in Narayanganj yesterday.

All members of the tenant who rented a flat on the third floor of the building several months back also left the flat with its door open.

Police suspect fraudsters, posing as tenant, might have made away with the valuables after rendering the victims unconscious by offering the victims food tainted with sedative.

The amount of cash or jewellery stolen by the gang could not be assessed as the victims are currently in the hospital and not in a state to explain as to what had happened, said Inspector (investigation) Mohammad Shahjalal of Fatullah Model Police Station quoting other tenants of the house.

Another tenant of the building found the door of the house owner's first floor flat wide open and the flat strewn with furniture and other belongings when he went there in the morning to inform the owner of a water shortage in the house, Inspector Shahjalal said.

The tenant, Tofail, who lives in a flat on the ground floor, also found several of the family members of the house owner were lying unconscious while some others were vomiting. He then rescued the victims with the help of locals and sent them to Dhaka Medical College Hospital, added Shahjalal.

The victims are house owner Ali Ahmed, 65; his wife Amirunnessa, 50; their daughters Jotsna Begum, 35, Kamarunnahar 30, Salma 22, and Habiba, 19; and Ali Ahmed's grandchildren Nur-e-Jannat, 5, Ali Hossain, 9, and Sumaiya Akter, 5.

When searched, only a handful of light furniture were found inside the new tenant's vacant flat on the third floor. Other tenants of the building have no knowledge about the new tenant, Inspector Shahjalal said.

Leftovers of expensive food including roasted chicken, beef, pulao, and sweets were found on the table inside the house owner's flat, he said, adding that the fraudsters might have fed the sedative-tainted food to the house owner's family on Tuesday night.  

Shah Md Manzur Quader, officer-in-charge of the police station, said the criminals, presumably the tenant of the top floor flat, appears to have executed a pre-planned crime. Necessary action will be taken after the house owner and his family members return from the hospital.