A high school teacher was arrested on Wednesday on charges of murdering his 13-year-old student and cutting her body into pieces, which were found packed in a nylon sack in an irrigation canal near Rampurhat in Birbhum district on Tuesday night.

The decomposed body of the Class VII student was recovered 20 days after the tribal girl had gone missing while on her way home from private tuition.

The additional chief judicial magistrate’s court in Rampurhat remanded Manoj Kumar Pal in police custody for nine days. The investigators have begun a detailed interrogation of the accused teacher, who is in his late 40s, to determine the motive behind the crime.

“The arrested teacher has confessed to the crime, and we have gathered some evidence. The actual motive, however, is yet to be established. The court today granted nine days of police custody of the accused, and during interrogation, we hope to uncover the reason and other details,” said Birbhum district police chief Amandeep.

A senior police officer said that the family identified the body from the girl’s face. However, they suspect that some parts of the body may still be missing. “During interrogation, we will verify whether the accused hid parts of the body at different locations to destroy evidence,” the officer added.

According to family members, the girl left her home early on the morning of August 28 for private tuition with a different teacher. When she failed to return, her father went to the school to check if she had gone there directly from tuition.

“When I went to the school, the headmaster told me that my daughter had not come. I lodged a complaint with Rampurhat police station that evening after failing to trace her,” said the bereaved father, a marginal farmer from the tribal community.

Saikat Hati, assistant public prosecutor of Rampurhat court, said the police had initially registered a case of kidnapping based on the family’s complaint. “After her decomposed and mutilated body was recovered from the canal, police booked the teacher for murder and destruction of evidence under sections of the Bharatiya Nyaya Sanhita (BNS),” he said.

The incident sparked protests, with villagers, including a large number of women, gathering outside the Rampurhat police station. They demanded that the accused be handed over to them and given capital punishment. Many alleged police negligence, accusing officers of failing to act for 20 days despite the family’s complaint.

Rampurhat subdivisional police officer Gobinda Sikdar and IC Sukamal Ghosh met the protesters and assured them of a thorough investigation to ensure justice.

The villagers also alleged that the teacher had raped the girl before killing her. Pal, a resident of Purulia, was a permanent teacher at the high school. Police sources said he had separated from his wife a few years back and lived alone in a rented house near the school.

“We are not ruling out any motive. However, the body was badly decomposed. However, it would take time to determine if the girl was raped before being killed,” said a senior officer.

The Opposition also questioned the police’s delay in recovering the body.

Sanjib Barman, CPM district secretariat member in Birbhum, said: “The incident is deeply unfortunate. A minor girl lost her life because of her teacher. But the bigger question is: what were the police doing for 20 days? Had they acted promptly after the family’s complaint, her life might have been saved.”

A senior Birbhum police officer denied the charge. “Top officers, including the SDPO and IC, were involved in the case from the very beginning. Investigations can take time. There was no lapse on our part,” said the officer.

The BJP alleged that the case reflected rising atrocities against women under the Trinamool Congress rule.

“Women are not safe in Bengal under Mamata Banerjee. Now, even minor girls are being targeted. Similar cases have been reported from Nanoor. This is a disturbing trend and Trinamool must take responsibility,” said Birbhum BJP president Dhurba Saha.

Trinamool district vice-president Malay Mukherjee countered: “It was an unfortunate incident, but the BJP has no right to speak on atrocities against women, given the countless such cases in BJP-ruled states. In this case, police have already arrested the accused.”