BERLIN (AP) — Rescuers are working to recover a man stuck deep inside a cave in the German Alps after he was injured by falling rocks. Police say the effort could last days.

A four-member rescue team reached the 52-year-old German cave researcher early Monday inside the Riesending cave system, near Berchtesgaden in Germany's southeastern corner.

He had suffered head and upper body injuries a day earlier. One of his two uninjured companions made a 12-hour climb back to the cave entrance to alert authorities, while the other stayed with him.

Police in the nearby city of Rosenheim said rescuers had set up bivouacs inside the cave system on the border with Austria. They said more cave rescue specialists were being brought to the scene to bring the man out.