(NEXSTAR) – An American speleologist exploring the Morca Cave in Turkey is currently trapped at a depth of more than 1,000 meters after becoming ill during the expedition.

Mark Dickey, 40, was co-leading an expedition on Saturday, Sept. 2, to map new passages within the Morca Cave — Turkey’s third-deepest — when he became “severely ill,” according to Gretchen Baker, the National Coordinator of the National Cave Rescue Commission (NCRC), an all-volunteer organization based in Huntsville, Alabama.

Dickey, from New York, is the NCRC’s international exchange program coordinator, and has been teaching instructional classes on cave-rescue techniques for 10 years, Baker told Nexstar.

“Currently, Mark is improving and is not as sick,” said Baker, who did not provide additional details on the cause of Dickey’s illness.

The European Cave Rescue Association (ECRA) provided slightly more information, publicly stating that Dickey had experienced a bout of “severe gastric pain” at a depth of around 1,040 meters.

“He [had] gastrointestinal bleeding and when the report was received, he was clearly unable to leave the approximately 1,000-meter deep cave on his own,” the ECRA wrote. (Baker said it would take an experienced spelunker around 15 hours to exit the cave from Dickey’s position.)

Rescue crews from Hungary descended to Dickey’s location on Sunday to set up a tent and provide emergency care, the ECRA wrote. This included emergency blood transfusions, a representative for Hungary’s team told the Associated Press. His circulation has since “stabilized,” the ECRA confirmed.

Additional teams from Turkey, Bulgaria, Croatia, Italy, and Poland are assisting with the rescue, the outlet reported.

Baker told Nexstar that the NCRC estimates the rescue to take between four and eight days, as the Turkish-led rescue teams will need to enlarge “some of the tightest passageways” in the cave to accommodate the stretcher that Dickey will need to be carried out on.

Yusef Ogrenecek, a representative for the Speleological Federation of Turkey, wasn’t quite as optimistic, telling the AP it could take weeks before Dickey is brought to the surface.

“Mark’s condition continues to improve,” the federation tweeted. “Doctors will decide whether it is possible for him to leave without a stretcher.”

The ECRA has set up a page for those who wish to donate to Dickey’s rescue efforts, and to the rescue teams directly.

“The leaders of the expedition asked for international help through Turkish federation of speleology and Turkish cave rescue, which are members of ECRA,” the organization wrote. “Rescue missions from such deepness are very rare, extremely difficult and need many very experienced cave rescuers.”

The Associated Press contributed to this report.