A group of Russian scientists plumbing the frozen Antarctic in search of a lake buried in ice for tens of millions of years have failed to respond to increasingly anxious U.S. colleagues — and as the days creep by, the fate of the team remains unknown. “No word from the ice for 5 days,” Dr. John Priscu professor of Ecology at Montana State University, told FoxNews.com via email. The team from Russia’s Arctic and Antarctic Research Institute (AARI) have been drilling for weeks in an effort to reach isolated Lake Vostok, a vast, dark body of water hidden 13,000 ft. below the ice sheet’s surface. The lake hasn’t been exposed to air in more than 20 million years.

Priscu said there was no way to get in touch with the team — and the already cold weather is set to plunge, as Antarctica’s summer season ends and winter sets in. “Temps are dropping below -40 Celsius [-40 degrees Fahrenheit] and they have only a week or so left before they have to winterize the station,” he said. “I can only imagine what things must be like at Vostok Station this week.” The team’s disappearance could not come at a worse time: They are about 40 feet from their goal of reaching the body of water, Priscu explained, a goal that the team was unable to meet as they raced the coming winter exactly one year ago.