Rescuers are rushing to save an American man trapped in the third-deepest cave in Turkey after he became ill, the Turkish Caving Federation said.

Some 150 rescuers are involved in a "complex" operation to save Mark Dickey, who was part of a research team in Morca Valley, the Turkish Caving Federation said. The rescue operation was first announced on Monday.

"In the Morca Sinkhole, the 3rd deepest cave in Turkey with a depth of 1,276 meters (4,186 feet), during an exploration mission involving local and international teams, American caver Mark Dickey fell ill at a depth of 1,120 meters (3,675 feet) and was placed under observation at the cave base camp located at 1,040 meters (3,412 feet)," the Turkish Caving Federation said on X, the platform formerly known as Twitter.

Bulent Genc, head of the federation, told CNN Thursday that the rescue could take days due to the fact that the cave is deep and narrow. Short movements will be required to carry Dickey out on a stretcher, Genc added.

Caving rescue workers from several countries have arrived in Turkey to assist in the operation, including Hungarian, Italian, Croatian and American rescuers, according to Genc.

The Hungarian Cave Rescue service said that Dickey suffered gastrointestinal bleeding.

Six units of blood were delivered to him, said the Turkish federation. His condition is currently stable and he is able to walk on his own, the federation added.

"Mark is currently residing at the campsite at 1,040 meters from the entrance," the Turkish Caving Federation said on Wednesday.

"The cave features narrow winding passages and several rappels," the federation said, adding that it takes 15 hours for an experienced caver to reach the surface in ideal conditions.

A rescue mission at this depth is "very rare, extremely difficult" and needs "many very experienced cave rescuers," according to the European Cave Rescue Association (ECRA), which is involved in the operation.

The association received a call on Saturday to report that Dickey was suffering from severe gastric pain.

On Sunday, a team from the Hungarian Cave Rescue Service, including a doctor, descended into the cave and set up a tent providing intensive medical care, the ECRA said.

On Monday, 17 people including a doctor and a paramedic from the Bulgarian rescue team reached the base site of the cave.

On Wednesday, Italian Croatian and Polish teams were on their way to the base camp.