The explosion occurred at the Ummal Qura International Madrasa, bdnews24 reported, quoting police. Explosives and bomb-making materials were later recovered from the premises.

Local residents told the news portal that the madrasa accommodates around 50 students. However, classes were not being held on Friday as it was the weekly holiday.

The blast was powerful enough to cause cracks in a neighbouring building, its owner said.

Residents said the building had been rented for the past three years by a man identified as Mufti Harun, who initially ran the madrasa before handing over its management to his brother-in-law, Al Amin.

The property owner, Parveen Begum, said she was unaware of any illegal activities being carried out under the cover of the madrasa.

“When I went there on Friday, I saw that the area around the building had been blown apart,” she told bdnews24.

Keraniganj Police Superintendent Mizanur Rahman said the cause of the explosion had not yet been determined.

“We are still investigating how the blast occurred,” he said.

The incident comes amid heightened tensions in Bangladesh, with the country witnessing a fresh spate of violence following political instability and the recent death of anti-India leader Osman Sharif Hadi.

Meanwhile, unidentified miscreants attacked and vandalised the Shah Sattyapir Mazar and dug up several graves in Thakurgaon Sadar upazila on Saturday.

Enamul Haque, president of the shrine committee, told The Daily Star that devotees regularly conduct religious activities at the shrine and that no “immoral activities” have ever taken place there.

“Yet unidentified miscreants vandalised the shrine and damaged several graves in the dead of night,” he said, adding that those responsible must not be spared.

He said preparations were underway to file a case in connection with the incident.

Md Monir Hossain, Officer-in-Charge of Thakurgaon Sadar Police Station, told the newspaper that police have launched an investigation into the vandalism.