Zvyozdochka, part of the Unified Shipbuilding Corporation, that specialises in repairs and recycling of nuclear submarines, said it had signed a contract with the Indian Defence Ministry in 2010 to carry out maintenance and upgrade the submarine. The craft arrived there in August.u00a0

The submarine, which exploded after a fire on board and sank in a Mumbai dockyard early today in which 18 personnel, including three officers, may have been killed, was upgraded and it sailed to Mumbai in January, 2013.