The Indonesian origin woman and her eldest daughter, who were found dead along with two other siblings in Gazipur's Sreepur, might have been raped before they were killed, said police after collecting evidence involving the killing.
Md Ekhlas Forazi, sub-inspector at Shreepur Police Station, told the Business Standard on Friday that police presumed they were raped before murder.
It seemed the miscreants killed them with sharp weapons as per their plan, he added.
The victims are Smrity Fatema, wife of a Bangladeshi expat Kajol Miah, their daughters Sabrina Sultana Noora, 16, and Haorin Hawa, 12, and their speech impaired son Fadil, 8.
Kajol's father Abul Hossain on Friday filed a case against anonymous miscreants in this regard. Police yet to arrest anyone.
Kajol Miah, a resident of Gafargaon upazila in Mymensingh, is currently working in Malaysia and his wife and the children lived in their two-storey home at Telihati union, said Kajol's elder brother Arif.
On Wednesday evening, Fatima asked Arif to buy her some essentials from market.
Arif, while going to the market the next morning, called out from outside Fatima's house but getting no reply left thinking everybody was asleep.
Around noon when Arif left home to go to the market again, he went to Fatima's home and called out again. Getting no response, he climbed a ladder, which he found on the back of Fatima's house, to the second floor and found the back door of the floor open.
He entered the floor and found the bodies Fatima and her children with their throats slit.
He also found the bodies with no clothes on them.
Informed, police rushed to the spot and recovered a blood stained knife and local weapon from the house.
Gazipur Additional Police Superintendent Md Rassel Sheikh said a team of seven members from forensic and crime scene units of Criminal Investigation Department (CID) Bangladesh visited the spot and collected various evidence of murder.
Police, PBI and RAB are investigating the murder.
The bodies of the victims were sent to a hospital for autopsies.
The preparations for the burial of the victims were underway at village Golabari in Mymensingh, the home district of the victims, said Kajal's nephew Mehedi Hasan.
"Bodies of the mother and her daughters had no clothes on them. We found a dagger and a knife at the spot," said Liakat Ali, officer-in-charge of Sreepur Police Station.
"Initially we believe that more than one person are involved in this incident but the motive of the murder is still unknown. We have sealed off the house and called the CID forensics department," he said on Thursday.