A blast sent thick black smoke into the air, shaking Bolpur in West Bengal’s Birbhum district on Wednesday. However, there is no reason for panic as the quake was the effect of the Indian Army personnel defusing a World War II-era mortar shell, recovered from one of the banks of the Ajay river a month back.

A month ago, residents of Laudah village under the Singi Panchayat in Bolpur police station limits had spotted a large bomb-like object lodged in a sandbank of the river. They brought it to the riverbank. After being informed, the Bolpur police reached the spot, and confirmed that it was an old shell believed to date back to World War II.

The area was cordoned off and guarded for weeks until Army assistance arrived.

It took time for bomb squad representatives to figure out how to defuse the shell. On Wednesday morning, a bomb disposal team from the Indian Army’s Panagarh camp reached the site. Soldiers first dug a deep canal in the Ajay riverbed and surrounded the shell with sandbags, before carrying out a controlled explosion.

Residents, initially terrified by the magnitude of the quake, later expressed relief that it had been safely neutralised. Minor damage to nearby agricultural lands was reported and a large crater formed at the explosion site.

Malay Mukherjee, a former professor in the Department of Geography at Visva-Bharati University, said, “Earlier, such shells were used by the British Army for military exercises. Many of these may have washed downstream during the floods in the Ajay river over time. This one too was likely from one such military exercise.”