PLEASE NOTE: EDIT CONTAINS CONVERTED 4:3 MATERIALbr br At least two people have been killed and 12 injured in an explosion that reduced a nine-storey apartment block to rubble in the Russian city of Astrakhan on Monday (February 27).br br Rescue teams have been sifting through the wreckage for 11 people still unaccounted for.br br The force of the explosion initially blew away the lower floors but the upper section of the building collapsed later.br br The exact cause of the blast is not yet known but a gas leak is most likely to blamebr br Russian Prime Minister Vladimir Putin has spoken to city officials and ordered the formation of a government commission to investigate the incident.br br The wrecked apartment block was part of a housing complex in Astrakhan, 1, 300 kilometres southeast of Moscow.