Rescue divers are continuing efforts to find survivors of an explosion aboard an Indian submarine in Mumbai, despite the increasing odds that none of the eighteen crew members will be found alive.

Near midnight Tuesday night the ship – the INS Sindhurakshak – suffered an explosion that. According to officials, the explosion appears to have damaged the forward torpedo tubes, which allowed water to come flooding into the ship. Efforts to fight the subsequent fire resulted in even more water coming into the ship, causing it to sink.

Three crew members were on the top of the ship when the explosion happened, and were able to escape into the water. They were rescued and taken to a nearby naval hospital and treated for minor injuries. The remainder of the crew – fifteen sailors and three officers – were trapped on board the ship.

Rescue efforts have been significantly hampered by the ship’s proximity to shore. The sinking stirred up a great deal of debris from the bottom of the harbor, reducing visibility in the water around the ship nearly to zero. Divers surveyed the exterior of the ship for before prying their way into the conning tower. There has been no contact with the crew since the sinking.

The Sindhurakshak – pictured above in better days – is a 16-year-old Kilo-class diesel submarine originally built in Russia. It recently returned from Russia, where it underwent a significant refit. Russia has become a major supplier of military equipment – including submarines – for India. The Indian navy is already short on submarines – only about half of the country’s tiny submarine fleet is currently active – and the sinking of the Sindhurakshak leaves them even more shorthanded. India is currently in the process of building up its navy due to concerns over China’s increasing naval power in the region.

Admiral D.K. Joshi, the Indian navy’s chief of staff, told reporters today that the explosion had occurred in the forward area of the ship. That section is home to the ship’s ordnance and batteries. While Admiral Joshi declined to speculate on the cause of the explosion, he did point out that the ship’s batteries had been finished charging for several days and that a hydrogen leak from the batteries was highly unlikely.

Once the survey of the outside of the ship is finished, rescuers will begin pumping out water in order to reduce the ship’s weight, making it easier to bring the ship to the surface.

While the situation is grim for the sailors still aboard the Sindhurakshak, Joshi insisted that there was still a chance that at least some of the men are still alive. “There have been instances where people have survived in the worst of conditions. We have not lost hope.”