Doctors have reached a badly injured German explorer in an Alpine cave and will soon start the process of bringing the 52-year-old researcher back to the surface, officials said.

Transporting Johann Westhauser through a series of five camps built throughout the cave system and eventually up to ground level could take as long as a week, NBC News reported. Two doctors are with the man, whose head was severely injured by falling rocks while he was exploring more than 3,000 feet beneath the surface.

"This is an important milestone, but it's only one of many," Stefan Schneider of Bavaria's mountain rescue service said of bringing the doctors to Westhauser, as quoted by NBC News.

The researcher has been trapped since Sunday inside the Riesending cave system near the town Berchtesgaden in southern Germany, according to the Associated Press.

The rock fall happened when Westhauser was spelunking with two colleagues around 20,000 feet from the cave's entrance. He stayed stable despite his injuries and was able to communicate with rescuers, who climbed for 12 hours and first reached him on Monday.

Through the care of doctors, Westhauser's body temperature has been kept at a normal level even though the cave stays at around 40 degrees Fahrenheit.

"Normally, the patient would now be in an intensive care unit, but inside the cave that level of care is impossible to achieve," Michael Petermeyer, a doctor working with rescuers, said at a press conference on Wednesday, as quoted by NBC News.

"The cave environment is already very dangerous for a healthy person," Petermeyer said.

A team of 30 rescuers from Germany, Austria, Italy and Switzerland have been working on the evacuation, the AP reported.

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