A low-intensity blast took place inside a medicine shop in West Bengal's North 24 Parganas district on Sunday afternoon, police said.
However, there has been no report of any casualty in the incident in Kamarhati area, they said.
A bag kept inside the shop went off around 1 pm. Preliminary investigation suggests some illegal firecrackers were inside the bag, a senior police officer said.
"A team of forensic experts will soon visit the spot. We have registered a suo motu case and started an investigation," he added.