A total of 6,489 people were evacuated as of 10 p.m. on Tuesday from the town of Chapayevsk, Samara region situated near the Volga State Ammunition Test Range where projectiles stared to explode on Tuesday, the regional department of the Russian Emergency Situations Ministry reported.

"As of midnight of Wednesday 85 people were lodged at deployed tents. Others have stayed with their relatives," the department said in a statement.

There are several theories of what happened, the Samara region governor's press service told Interfax.

"May be a human factor. Another theory is because of heat. Projectiles produced in 1940-s - 1960-s are stored at the range. It has been hot for several days. May be that was the influence of the weather," the press service said.