The dramatic rescue of an injured American researcher who became stuck in a deep cave in Turkey is about one third complete, officials said Sunday.

Mark Dickey, 40, became ill in the Morca cave in the Taurus Mountains on Sept. 2. He was vomiting and bleeding internally from his stomach, leaving him without any strength for the journey back to the surface.

The following day, his fellow cave explorers across the world began organizing a complicated rescue operation. When Dickey called for help, he was 3,400 feet deep in the cave. By Sunday morning, he’d been helped to an emergency camp about 2,300 feet from the surface.

“At this stage, he will set out again after resting and having the necessary treatments,” the Speleological Federation of Turkey said Sunday.

The rescue operation will feature multiple stops at the emergency camps in the cave, created so Dickey has opportunities to rest throughout the arduous journey back to civilization.

Observers described Dickey as an experienced cave explorer who was not out of his depth in the Morca cave, estimated as the third deepest in Turkey.

“The cave is made up of many vertical shafts, so many sections that are extremely vertical with few horizontal sections,” said Federico Catania, a spokesman in Rome for Italy’s National Alpine and Speological Rescue.