A powerful blast ripped through an explosives demolition ground near the Central Ammunition Depot in Maharashtra’s Wardha district, leaving six persons dead and 10 injured as workers unloaded ammunition for destruction of unserviceable ordnance on Tuesday.

The dead included an ordinance factory employee from Jabalpur, identified as Udayveer Singh. The rest were labourers hired for the job.

Inspector-general of police (Nagpur range) K.K.M. Prasanna said four persons died on the spot, while two succumbed to injuries in hospital. “Four of the 10 injured are critical.”

Sources said the 7am blast in Pulgaon, about 90km from Nagpur, took place while a box containing ammunition was being kept in a pit dug for the controlled destruction.

Rameshwar Badhiye, a local resident, said the blast happened “after one of the boxes fell while being unloaded”.

The ordnance depot in Wardha stocks weapons and explosives produced at ordnance factories across the country before they are sent to other army bases.

The ammunition being destroyed were shells for the Russian-made 23mm Shilka anti-aircraft system. The ordnance factory at Khamaria near Jabalpur, Madhya Pradesh, had been manufacturing the shells before production was halted in 2014 following reports of accidents while handling the rounds.

A defence source said the ground near the ammo depot has been used for such controlled destruction for years. “A contractor was engaged for digging the pits and placing sandbags. The labourers were hired by the contractor.”

In May 2016, 18 people, including two army officers, died after a fire broke out in a warehouse for anti-tank mines at the depot following a leak.