The investigation into the killing of a retired teacher and three members of his family in Rangpur has been handed over to the Detective Branch (DB) of police after questions raised over the police account of the incident.

The investigation was transferred to the DB to ensure a more transparent and comprehensive investigation and to facilitate the submission of a charge sheet quickly, said Rangpur Metropolitan Police Deputy Commissioner (DB) Sanatan Chakraborty on Tuesday.

The case was previously being investigated by the Kotwali Police Station.

Inspector (Investigation) Milan Chatterjee of Kotwali Police Station went to the DB office and handed over the case documents and relevant information to the new investigating officer, Inspector Zinnat Ali on Monday, said police.

Later, the two officers visited the house of retired teacher Ganapati Chakraborty in Machuapar, where the four bodies were recovered.

Sanatan Chakraborty said two accused made confessional statements before a court under Section 164 of the Code of Criminal Procedure on Sunday night.

The decision to transfer the case investigation came after widespread questions were raised over the police's initial explanation of the killings.

During a press briefing, Rangpur Metropolitan Police Commissioner Mohammad Abdul Mabud on Sunday said Ganapati Chakraborty, his wife, son and daughter were killed after the retired teacher confronted two youths who had gone to the roof of his house to consume Yaba pills.

The statement triggered questions among relatives of the victims, local residents, teachers, students and other citizens.

They demanded a more comprehensive investigation and held human chains and protest rallies.

Police said the new investigation officer would examine every aspect of the case, verify the available evidence and information, and take further legal action accordingly.