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A cave and mountain rescue expert from Germany, second left, talks to his colleagues after his descent into the Riesending cave on the Unterberg mountain near Marktschellenberg, Germany, Wednesday, 11 June 2014, where a 52-year-old renowned professional cave explorer was caught in an underground rockslide in the early hours of June 8, 2014. Germany?s mountain rescue service says medics are hoping to within hours reach the researcher stuck deep inside the Alpine cave on the Austrian border. (AP Photo/dpa, Tobias Hase)

BERLIN (AP) — Rescuers say a 52-year-old German explorer who was injured in a fall deep inside an Alpine cave is well enough for the evacuation process to begin.

Researcher Johann Westhauser has been stuck 1,000 meters (3,280 feet) underground since suffering head injuries in a rock fall Sunday inside the Riesending cave system near the town Berchtesgaden in southern Germany.

The head of the rescue operation says doctors have given the OK for Westhauser to be stretchered out, a difficult process that will take days because of the narrow shafts and vertical lifting involved.

Andreas Wolf said Thursday that some 30 rescuers from Germany, Austria, Italy and Switzerland are in the cave preparing the evacuation.

Westhauser was spelunking with two colleagues when the rock fall happened some 6,000 meters from the entrance.