The fate of 18 sailors on board an Indian navy submarine hit by explosions was unknown Thursday, as divers carried out search and salvage operations in a bid to find survivors, DPA reported. The 18 sailors - including three officers - were on board the newly upgraded kilo-class INS Sindhurakshak submarine when it was hit by the explosions at the naval dockyard in Mumbai shortly after midnight on Wednesday. Navy divers entered the vessel by prizing open a jammed hatch but found no signs of life, NDTV news channel reported Thursday. A navy-appointed probe into the accident was looking at whether it was caused by human error or defective materials, NDTV reported.