Two small, manned submarines reached the bottom of Lake Baikal, the world's deepest freshwater lake, on Tuesday, Russian news reports said.
The "Mir-1" and "Mir-2" submersibles descended 1.05 miles to the bottom of the vast Siberian lake, reports said.
Scientists on board will take samples of water and soil from Lake Baikal, which is home to more than 1,700 species of plants and animals, reports said. They also will plant a small pyramid bearing the Russian flag in the lake bed, reports said.
Russian news agencies earlier cited organizers as saying the expeditions set a world record for the deepest descent in a freshwater lake. State Duma deputy and expedition leader Artur Chilingarov later said no such record was broken Tuesday, the Interfax news agency said.
Mission chief Anatoly Sagalevich said the mission will make a total of 60 dives. Organizers then will compile a list of recommendations at how best to preserve Lake Baikal, a UNESCO World Heritage site.
Last August, the "Mir-1" and "Mir-2" descended below the North Pole, with Russians on board planting their country's flag in a titanium capsule on the Arctic Ocean floor to symbolically claim the seabed.