The incident occurred around 9.30 am when the policemen selected for the city police’s Special Action Force (SAF) were undergoing a mock drill on how to react during a blast-like situation.

Mishra sustained splinter injuries on his leg and just below his left eye while Mitra received minor injury.

A police officer at the Alipore Bodyguard Lines said during mock drills, stunt grenades, which create more smoke and sound rather than causing damage, are used.

He said for the last few days, the selected personnel used bricks instead of stunt grenade and today when they started the mock drill with stunt grenade, the explosion occurred. Several senior officers of Kolkata Police were present during the mock drill and they were also surprised with the explosion of the stunt grenade.