Ramna police arrested Shitu, the lone accused in the first information report (FIR), on the second floor Nayatola flat opposite Sadman's.

Unknown assailants picked up Sadman, also known as Arian, in the morning opening the latched door of their flat before strangling him and dumping his body in the attic of the apartment block in a trunk.

His body, wearing multiple injury marks, was found in the afternoon and his relatives believe somebody living in the same apartment block killed the child.

Police picked up Shitu on Thursday after Selim Sarker, father of Sadman and a receptionist of Monwara Hospital in Ramna, filed a case with Ramna Police Station the same day.

Producing her before the court yesterday, police filed a five-day remand petition, but the court granted two days.

Police are also grilling Mariam, home help of a third floor flat of the same building, after arresting her on Wednesday.

The court remanded her in two-day police custody on Thursday.

"Both women need to be properly quizzed to see whether they had any involvement in the killing," Sub-Inspector Fazlul Haq of Ramna Police Station, who is currently probing the case, said yesterday.

"I've talked to the landlord's family and all the tenants of the building to find out who were present and doing what during the killing."

Asked about the motive for the killing, he said, "I need time to find it out as the murder was carried out is a very planned way."