New Delhi (CNN) -- Four severely burned bodies have been recovered from an Indian navy submarine that sank in Mumbai this week after an explosion and fire on board, authorities said Friday.
The Indian government warned that there was almost no hope of finding any survivors among the 14 other sailors who were in the submarine when it was hit by the unexplained blast at a naval dockyard early Wednesday.
Navy divers have been searching for the trapped submarine personnel for the past two days.
Their task has been complicated by poor visibility inside the stricken submarine's passageways, which are full of oily, muddy water and wreckage. Adding to their difficulties, the heat of the explosion warped some of the hatches inside the vessel, blocking the divers' access to certain areas.
The four bodies they found Friday are unidentifiable because they were so severely burned, authorities said. They have been taken to a naval hospital for DNA identification.
Searching 'every inch'
The state of the bodies and conditions inside the INS Sindhurakshak, a Russian-built submarine, mean that "finding any surviving personnel within the submarine is unlikely," the ministry said.
"The feasibility of locating bodies of personnel in the forward part of the submarine is also very remote, as the explosion and very high temperatures, which melted steel within, would have incinerated the bodies, too," it warned.
But divers will continue to scour "every inch" of the submarine until all the bodies are recovered "or it can be stated with finality that no bodies remain to be found," the statement said.
Authorities say they have contacted the families of all the 18 missing personnel and are keeping them updated. The defense ministry has published the names of the three officers and 15 sailors concerned.
Worst peacetime disaster
An investigation into the explosion and fire -- the Indian navy's worst peacetime disaster -- is under way. Navy officials say they so far can't pinpoint the cause.
Salvage work on the diesel-electric submarine won't begin until the search for bodies is over, the defense ministry said Friday.
The Sindhurakshak had only recently returned from an extensive refitting in Russia before the disaster.
Observers have described the vessel's sinking as a significant setback to the navy's ambitions.
It took place just days after two events hailed as big steps forward for the Indian military's technological capabilities.
The Indian navy had last week activated the reactor on the Arihant, its first domestically built nuclear submarine. And on Monday, it launched the Vikrant, a home-built aircraft carrier.
CNN's Harmeet Shah Singh reported from New Delhi, and Jethro Mullen reported and wrote from Hong Kong.