Russian scientists have drilled into the vast, dark and never-before-touched Lake Vostok 2.2 miles below the surface of Antarctica, the state-run Russian news agency RIA Novosti said Monday.

“Yesterday, our scientists stopped drilling at the depth of 3,768 meters and reached the surface of the subglacial lake,” the news agency quoted a source as saying. The team had “finally managed to pierce” the ice sheet into Vostok, the source said.

The report could not be verified Monday, but numerous Antarctica experts in the United States said they were hearing the same unconfirmed news. Sergei Lesenkov, spokesman for the Arctic and Antarctic Scientific Research Institute, told Agence France-Presse in Moscow on Monday that there was the possibility of a “fundamental scientific development.”

It has taken the Russians more than 20 years to drill into the lake, operating in some of the most brutal weather conditions in the world.

Many scientists see Vostok as not only a last frontier on Earth, but also a potential gold mine for learning about possible conditions on Jupiter’s moon Europa or Saturn’s moon Encedadus. Each is covered by a thick shell of ice with liquid water below, warmed by either the inner heat of the moon or by tidal forces.

The United States and Britain will begin drilling later this year into small subglacial Antarctic lakes. Scientists estimate there are about 200 of these lakes beneath the ice sheet.