Numerous strong explosions rocked Chapaevsk and several villages around on June 18, 2013.
The detonation injured about 30 people and causing the evacuation of more than 6,000 from a nearby village.
The cause of the mystery remains unclear although officials say it was set off by the “involuntary” explosion of shells.
The emergency ministry said about 30 people had sought medical help and 11 of them were taken to hospital.
More than 6,000 people were evacuated from the village of Nagorny.
Russian munitions, which frequently date back to the Soviet era, have exploded several times in recent years, the latest case being near the town of Achinsk in the Siberian region of Kraskoyarsk in August 2019.
