Without examining the bow of the boat, it is impossible to completely clarify the cause of the disaster

Vladimir Ustinov Russian Prosecutor General

Once the initial inspection has been carried out, the crucial task remains of dismantling the two nuclear reactors and the 22 cruise missiles that were the Kursk's main armament.

Toxic gases

The BBC's Stephen Dalziel in Moscow says the smashed windows and broken cables visible from the outside are just a small indication of the chaos which the 40-strong team expects to find when it enters the wreck.

The wreck was dragged into dock by a giant barge

The investigators will have to don protective suits and gas masks since toxic fumes have built up in the vessel during its 14 months at the bottom of the sea.

Prosecutor General Vladimir Ustinov says his team will be on the look-out for journals and notes taken by crew members, and has warned that if any senior naval officers are found guilty of causing the loss of the Kursk, they will "bear responsibility regardless of their years of service".

The green light for the investigation was given after the wreck was detached from a giant barge which had towed it into dry dock in the Arctic port of Roslyakovo after it was lifted from the bed of the Barents Sea earlier this month.

Salvage to continue

But Mr Ustinov admits that the inquiry will eventually have to focus on the bow of the Kursk - still to be removed from the seabed.

"Without examining the bow of the boat, it is impossible to completely clarify the cause of the disaster," he said before leaving Moscow.

The Russian authorities have said they will try to recover the bow next year. But Vice-Admiral Mikhail Barskov, the officer charged with the recovery of the Kursk, has already said it is in such a poor condition it cannot be lifted as a whole.

The bow had been cut from the main part of the Kursk because of the danger posed by the torpedoes. Some experts believe that the explosions which destroyed the submarine probably originated there.

Theories to explain the disaster include the explosion of a faulty torpedo in the bow and a collision with another submarine or old anti-shipping mine.

One contentious theory, carried by some Russian and German media, is that the submarine was hit by a missile fired in error by a Russian warship during exercises.