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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) — Germany's mountain rescue service says doctors are close to reaching an injured explorer stuck deep inside an Alpine cave on the Austrian border.

Researcher Johann Westhauser was injured in a rock fall Sunday 1,000 meters (3,280 feet) underground, inside the Riesending cave system near Berchtesgaden.

Rescue official Robert Nagel said Wednesday that two doctors are on their way to the site of the accident, some 6,000 meters from the entrance.

He says they could reach Westhauser within hours and will then assess how the 52-year-old German can be brought to the surface.

Nagel says the tricky terrain within its vertical shafts and narrow passages means it will take about six days to bring Westhauser out.

Westhauser had been spelunking with two colleagues. A team of experts reached him on Monday.