General Prosecutor Vladimir Ustinov made the announcement after meeting with Russian President Vladimir Putin, who ordered the prosecutor to inform the Russian public about what caused the explosion.
"The disaster occurred at 11:28 and 26.5 seconds Moscow time because of a blank torpedo explosion inside the fourth torpedo tube, which in turn triggered explosions in torpedo charge chambers in the submarine's bow section," Ustinov said, according to remarks shown on Russian television.
For two years, the Russian government had been reluctant to admit that its state-of-the-art submarine was destroyed by an internal malfunction. But earlier this month, a commission investigating the August 2000 disaster in the Barents Sea said that had become the only possible explanation.
Ustinov said everyone on the Kursk died within eight hours of the explosion.
Russia has already pulled from service all torpedoes of the type that malfunctioned, which uses the highly volatile fuel as a propellant and have reportedly been used since the early 1970s. The torpedoes have a higher speed and range than conventional torpedoes powered by electric engines.
The Kursk disaster — and especially the government's failed operation to rescue the sailors who initially survived the blasts, trapped inside the mangled submarine in the Arctic depths — drew massive criticism at home and abroad.
The ruined hulk of the submarine was salvaged and lifted out of the seabed last fall.
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