A rescue operation has begun to free 40-year-old Mark Dickey, an American scientist who’s been trapped in Morca Cave, the third-deepest cave in Turkey, since last Saturday, NBC reports. The Turkish Caving Federation says that due to the explorer’s injury, the operation will likely take several days. Dickey, who is currently 3,000 feet below the surface, fell in distress last week when he began suffering gastrointestinal bleeding, necessitating a rescue operation that’s ballooned to include over 150 people. “The caving world is a really tight-knit group and it’s amazing to see how many people have responded on the surface,” Dickey said last week in a video dispatch. “I do know that the quick response of the Turkish government to get the medical supplies that I need, in my opinion, saved my life. I was very close to the edge.”