LISTVYANKA (Irkutsk Region), June 15 (RIA Novosti) - Two Russian mini-submarines descended on Monday into Siberia's Lake Baikal, the world's deepest lake, as part of an ongoing research expedition.

One of the expedition's organizers, Oleg Zverkov, said the two mini-subs would go down to a depth of 700 meters (almost 3,000 feet) to study the lake's floor for about three hours, and could continue the dive if interesting discoveries are made.

"If they find something interesting today, they may spend more time underwater or may go deeper," Zverkov told RIA Novosti.

The expedition will focus on monitoring the lake's ecosystem, studying its flora and fauna, hydrothermal activity, and mud volcanoes on its floor, as well as seeking more precise data on tectonic processes under the lake.

Russian mini-subs conducted 52 dives last summer to study the lake's unique ecosystem and visited the deepest point of the lake, near the center off the island of Olkhon, with a depth of some 1,600 meters.

During last year's dives, a number of significant scientific discoveries were made. Notably, researchers took samples of oil that seeps through cracks in the lake's bedrock and is digested by the lake's organisms.

Many questions still remain unanswered, including the origins of the lake, believed to be 25 million years old, and the unique organisms that live in it.

The first dives this summer are taking place in the southern part of Baikal. In July, dives are planned in the center of the lake, and the expedition will move on northward in August.

The second stage of the $7.5-mln Baikal research project envisions over 100 deep-water dives this year, a Russian government official said last month.