Rescue teams in Turkey successfully carried American researcher Mark Dickey to the 2300ft (700m) mark on Sunday. He will rest there before they continue the journey to the surface.

The 40-year-old started vomiting on 2 September because of stomach bleeding while on an expedition in the Morca cave in southern Turkey.

The painstaking rescue involves teams pulling his stretcher through narrow passages and vertical shafts to the surface.

This could take up to 10 days, according to Recep Salci, head of the search and rescue department of Turkey's Disaster and Emergency Management Directorate, AFAD. If his condition improves, the mission could be faster.

Doctors, paramedics and experienced cavers rushed to Turkey to help with the mission. Turkish authorities said 190 people from eight countries are involved, 153 of them search and rescue experts.

Rescuers have set up small medical base camps at various levels along the shaft, providing Mr Dickey an opportunity to rest during arduous extrication.

One of the most difficult tasks of cave rescue operations is widening the narrow cave passages to allow stretcher lines to pass through at low depths, Yusuf Ogrenecek, of the Speleological Federation of Turkey, said.

"Stretcher lines are labour intensive and require experienced cave rescuers working long hours," he said.

Rescuers will also have to navigate through mud and water at low temperatures and deal with the psychological toll of staying inside a cave for long periods of time.

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Teams including a doctor and three or four others take turns staying with Mr Dickey at all times.

On Saturday, Mersin governor Ali Hamza Pehlivan said Mr Dickey was in a stable condition.

"We have received information that his condition is getting better, thanks to medical intervention," he said.

Mr Dickey is an instructor with the US National Cave Rescue Commission (NCRC). He is highly regarded in the international speleological (the study of cave exploration) community and has previously taken part in rescue missions.

He was co-leading an expedition to find and map a new passage in the Turkish cave, the third deepest in the country, when he fell ill.