Russian prosecutors on Tuesday said they've opened a criminal investigation into the accident that left seven crew members trapped in a mini-submarine (search) for three days in the Pacific Ocean.

An initial investigation has found violations by officials responsible for preparing and overseeing the AS-28 mini-submarine's mission, said Roman Kolbanov (search), the Pacific Fleet's deputy military prosecutor. Those findings led to the criminal inquiry, he said.

One of the submariners, Capt. Valery Lepetyukha, revealed Tuesday that the submarine had been sent to investigate an underwater surveillance antenna that got entangled in fishing nets.

Russia had to appeal for outside help to rescue the submarine, which was stuck 590 feet below the surface off Russia's (search) remote Pacific coast. A remote-controlled underwater vehicle called a Scorpio that was sent by Britain cut away the cables that had snarled the Russian vessel.

Pacific Fleet commander Adm. Viktor Fyodorov said Tuesday that the navy will buy two Scorpios. The vehicles cost anywhere from $1 million to $5 million each, depending on the configuration.

Moscow newspapers have criticized the navy as failing to learn the lessons of the 2000 Kursk submarine disaster, in which all 118 crew members died. The papers said the navy hadn't sufficiently upgraded its rescue capabilities and waited too long — a day — to report the most recent accident.

Kolbanov, the prosecutor, said experts from the Russian general staff, navy command, Defense Ministry, Federal Security Service and Finance Ministry would be involved in the investigation, as well as the company that built the mini-sub.

After the seven men were rescued, British Royal Navy Commander Ian Riches, who directed the Scorpio's work, said Russian officials had told him that only six hours of oxygen remained on the mini-sub.

However, Lepetyukha insisted Tuesday that oxygen supplies could have lasted another 36 hours, the RIA-Novosti news agency reported. He also denied that crew members had written farewell messages to their loved ones, as some Russian media have