ULYANOVSK, November 15 (RIA Novosti) - The explosion at a weapons depot in the Ulyanovsk Region in the Volga area that killed two people and injured many others was caused by the violation of ammunition disposal rules, the Russian Navy chief said on Sunday.

A series of explosions hit a Navy arms depot in the Volga city of Ulyanovsk on Friday night. Shockwaves from the explosions smashed windows in nine schools and 20 kindergartens. Due to damage to housing, 105 people have been placed in hotels, including 17 children.

"The cause for the explosion is the violation of the ammunition disposal techniques," Admiral Vladimir Vysotsky said.

Vysotsky said that the fire broke out in the places of arms disposal and not at arms storage facilities, adding that an investigation was yet to identify persons to blame for the tragedy.

Overall, about three wagons of artillery shells weighing over 100 metric tons were kept at the arms depot and about 40 tons of them exploded, the Navy commander said.

Twenty firefighting crews were called in to fight the ensuing blaze, which was put out during the night. Teams of sappers are currently at the site to clear the territory of unexploded shells scattered around the area.

Russian President Dmitry Medvedev ordered the government to conduct an investigation into the incident and safety checks at all the county's weapons depots.