MOSCOW - Buffeted by storms, Russian rescuers repeatedly tried Tuesday to lower an escape capsule to 116 sailors trapped in a crippled nuclear submarine sitting on the floor of the Barents Sea.
Two U.S. government officials said Tuesday in Washington that a Navy submarine in the area detected the sound of an explosion and it was the ''working assumption'' that the noise was related to the sinking of the submarine Kursk. The officials, who spoke to The Associated Press on condition they not be named, said the sound was not a missile being fired.
Russian Navy Chief Adm. Vladimir Kuroyedov said earlier Tuesday that there appeared to have been an explosion in the torpedo compartment in the nose of the submarine, sending it crashing to the sea bottom. He said earlier that the Kursk had likely collided with something and it wasn't clear why he had changed his assessment.
Efforts to rescue the Kursk were hampered most of Tuesday by high winds and strong currents.
There had been no communication with the submarine since it went down, and conditions inside were not known. It wasn't clear how much air the crew had left and water appeared to be leaking in, officials said.
Seizing on a break in the weather late Tuesday, rescue ships resumed efforts to lower the escape capsule, but rough weather was frustrating the operation. The situation, Kuroyedov said, was ''extremely grave.''
The rescue operation faced severe difficulties. The bell-shaped capsule was to try to latch on to a cargo hatch on the submarine, a precision maneuver made even more challenging because the Kursk was reportedly leaning at a sharp angle.
Even if the capsule successfully docks with the sub and sailors can enter it, the capsule can hold only 20 people at a time and officials say bringing it to the surface could take up to seven hours. The slow rise is necessary to prevent decompression sickness - the potentially crippling or fatal condition known as ''the bends.''
It would be a laborious and nerve-fraying process under the best of circumstances, and weather forecasts indicated conditions in the disaster area would be rough for several days.
Russia refused offers from the United States and Britain to send trained rescue personnel and equipment even though the Russian navy lacks sophisticated rescue gear. Navy spokesman Capt. Igor Dygalo said coordinating the rescue with other countries would take too much time and ''we cannot afford to waste it.''
However, a group of Russian military officers went to NATO headquarters in Brussels, Belgium, on Tuesday night to see what kind of assistance the alliance could offer, a NATO source said on condition of anonymity.
The U.S. officials said Tuesday that the sound of the explosion was detected Saturday. The Russian government has said the accident that brought down the Kursk happened Sunday during military exercises. The discrepancy could not be explained.
Pentagon spokesman Rear Adm. Craig Quigley declined to say what, if anything, U.S. vessels may have heard from their position ''a couple of hundred'' miles away from the place the sub went down.
An explosion inside the submarine's torpedo chamber, which contains warheads, would probably have caused extensive casualties, analysts said. Navy officials said casualties could not be ''ruled out,'' Interfax reported.
While immediate concerns focused on the crew, there was also worry over whether the accident would result in a leak of radioactive material. The prospects of such a leak were difficult to assess because it is not known what befell the Kursk, one of the Russian navy's most modern ships.
Russian officials said the Kursk's two nuclear reactors had been switched off and it was not carrying nuclear weapons.
Several compartments inside the submarine were flooded, officials said. Submarines are divided into compartments that can be sealed in case of flooding.
''Something extraordinary beyond the imagination of an engineer'' had happened, the chief designer of the submarine, Igor Baranov told the ITAR-Tass news agency.
Russian and Western submarines sometimes play cat-and-mouse games in the area and have scraped each other in the past. The U.S. Navy said Monday it had a monitoring ship in the area, but Quigley said there was no evidence that any U.S. vessel was involved in the accident.
Russian nuclear submarines have been involved in a string of accidents in recent decades. The navy, like the rest of the Russian military, is desperately short of money and performs almost no maintenance on its ships.
