On Wednesday morning, the decapitated body of Abir, 11, a Class-II student of Nurani Hafizia Madrasa and Orphanage, was recovered from a mango orchard of the village.
Additional Superintendent of Police Md Kolimullah said divers recovered the severed head from the pond around 10am.
Police said madrasa superintendent Mufti Abu Hanif might have been involved in the murder as his behaviour was found to be suspicious.
Citing other teachers and studetns, officer-in-charge of Alamdanga Police Station Asaduzzaman Munshi said Hanif was found anxious when he was saying Esha prayers on Tuesday night.
He also went out of the mosque for a while during the prayers, the OC said.
Meanwhile, police continued to interrogate five detained teachers of the madrasa over the murder.
At a press briefing on Wednesday, Superintendent of Police of the district Mahbubur Rahman claimed that the madrasa boy had repeatedly been molested which was evident in the postmortem report. "He might have been killed to hush up the matter."
Abir went missing on Tuesday night.