Military prosecutors have begun a criminal investigation into allegations that the Kursk collided with an unidentified vessel that later escaped, the Interfax news agency reported Saturday. Citing unidentified sources, Interfax said the prosecutors believe the vessel violated safety rules and was directly responsible for the sinking of the Kursk. 
A spokesman at the military prosecutor's office could not confirm the report Saturday. An investigation by the prosecutor-general's office had been announced previously. 
Russian experts have not conclusively determined what was responsible for two explosions aboard the Kursk, which went down Aug. 12 during military exercises in the Barents. Military officials claim the most likely scenario was that the Kursk collided with another vessel, most likely a foreign submarine. 
Both Britain and the United States denied their submarines collided with the Kursk. 
Interfax said the alleged vessel was being investigated for "violation of safety rules in the movement and use of rail, air or water transport, which resulted in the death of two or more people because of carelessness." 
Some observers say the most likely reason for the sinking was an internal malfunction and explosion in the submarine's torpedo compartment. Russian officials also have not ruled out the possibility that the Kursk hit a World War II-era mine. 
The cause of the disaster probably won't be known until experts study the shattered submarine more closely to see if it can be raised. Russia is negotiating with Norwegian and Dutch companies to bring up the wreckage. 
Russian officials have sought to quash concern around the world over the Kursk's two nuclear reactors. Officials say there is no sign of unusual radiation levels around the submarine, but there is growing concern that the reactors are not safe and may begin leaking. 
Many Russians accused the government of being slow to react to the sinking and of bungling rescue efforts. 
The disaster has been a grueling ordeal for the families, many of whom learned of the sinking from television reports , then endured days of a confused rescue operation, then only heard from Norwegian divers that all aboard were dead. 
Even Russia's handling of the bereaved relatives has drawn criticism. 
As CBS News Correspondent Richard Roth reports, when one woman wanted answers from a beleaguered bureaucrat, what she got was a tranquilizer a hypodermic pumped into her by a Navy medic. 
While a Russian psychologist says tranquilizer administration is an accepted Russian practice in such circumstances, to some the image illustrated the callous treatment families were receiving at the time. 
Some observers have said the allegation that a foreign vessel was responsible for the disaster is an attempt to deflect blame away from faults within Russia's poorly maintained and cash-strapped armed forces. 
During several days of attempts by Russian mini-submarines to dock with the sunken Kursk's aft escape hatch, officials said the hatch was severely damaged. But a Norwegian-British team of divers that eventually succeeded in opening the hatch said it was in good shape. 
"There was evidence of what looked liked cracking, but it turned out to be signs of regular movement of the rubber panels ... and that could be construed as damage," one of the divers, Tony Scott, told The Associated Press on Saturday. 
There are even reports that Russian officials stymied foreign rescue efforts when the sub first went down. 
"At times there were so many wrong details and disinformation from Russia that it was close to endangering the divers," said Norwegian Rear Admiral Einar Skorgen, who commands the armed forces in north Norway. "We couldn't rely on the information we were getting."