The injured were admitted to RG Kar Medical College and Hospital where they are stated to be out of danger. One of them, Partho Oraon has been discharged.

The bomb was in a tiffin box and most probably it was abandoned some time ago. In the morning, the workers were busy cleaning the drain, Belgharia Sub-Divisional Police Officer Ashok Roy told The Indian Express.

“When their cleaning equipment struck the bomb, it went off. As of now, we have no clue how the bomb got there and what was kind of the explosive used,” Roy said.

A 15-year-old boy, Pervez Alam, recounting the mishap said, “I was taking bath near the drain when I heard a loud explosion. At that moment, I had no idea what had happened. Later, I realised I was bleeding.”