MAE SAI, Thailand — Four members of a youth soccer team were removed Sunday from a cave complex in northern Thailand where they had been stranded for more than two weeks, as officials decided to use a dangerous rescue option amid the threat of rising water.
Eight of the boys and the coach remained inside the Tham Luang Nang Non cave, as authorities paused the emergency operation until Monday to replenish air tanks along the treacherous exit route.
‘‘The operation went much better than expected,’’ said Narongsak Osatanakorn, Chiang Rai’s acting governor, who is overseeing the mission. But he said it could take up to four days to evacuate the others, depending on conditions.
Narongsak said the four boys were checked out at a field hospital and then taken by helicopter to a hospital in Chiang Rai, the provincial capital, for evaluation Sunday. He said it would take 10 to 20 hours to resume the rescue mission.
An entire floor at the Chiang Rai hospital has been reserved for the recovery effort.
The players and their coach have been trapped since June 23 by floodwaters in a dark, six-mile-long cave system. The drama of the rescue, with all its peaks of euphoria and lows of anxiety, has gripped the world.
Heavy rains are about to fall over the lush mountain range that houses the cave, adding urgency to the rescue. Narongsak said new rain could shrink the unflooded space where the boys are sheltering to about 108 square feet.
According to a diagram released by the Thai government, two divers are being paired with each person being rescued. The rescued people are being fitted with face masks connected to a compressed air tank carried by divers.
At especially narrow parts of the cave, the tanks are released from the backs of the divers and rolled instead.
Officials have said that conditions Sunday were as good as they can be. The water levels in the cave are the lowest they have been throughout this mission, and the first few chambers that the group will have to pass through — all of which were flooded days ago — are now dry.
Oxygen levels, too, have stabilized after fears that the chamber the group was in was filling with carbon dioxide from members of the large rescue operation.
‘‘The kids are so strong, physically and mentally,’’ Narongsak said, although they are weakened and malnourished by their ordeal.
But experts have warned that extraction will bear significant risk, underscored by the death of Saman Gunan, a retired Thai navy SEAL, early Friday when he ran out of oxygen during a dive. He was placing compressed air tanks along the exit route when he fell unconscious and died shortly after.
This risk remains for other members of the team, who could run out of air supply before reaching safety, said Tony Haigh, a spokesman for the British Cave Rescue Council, two of whose members were the British rescue divers that found the boys.
‘None of the boys can swim, but they have been given extensive diving lessons since being found.’
Another risk is becoming trapped by an obstacle divers cannot see because their field of view will be limited in the muddy, brown water.
‘‘Clearly there is a huge risk of someone panicking if they are not used to the diving environment. It happens to adults in the open water, never mind children in a dark cave,’’ Haigh said. “None of the boys can swim, but they have been given extensive diving lessons since being found.’’
The young soccer players and their coach were trapped when monsoon rains flooded the cave while they were exploring. The group was found in a small cave chamber Monday — after nine days — launching a rescue effort of more than a thousand people.
The international team of divers assisting the effort are from the United States, Australia, China, and Europe.
Authorities for days had been stalling on a firm decision on the best path forward to extract the team.
Authorities said efforts to drill down from the top of the mountain have been unsuccessful. Impending rains made that option less viable, as it would take too long.
Narongsak said that rescuers have assessed the boys’ condition and also briefed their families, who are aware and supportive of the diving plan. Officials have been racing against the clock to get the boys physically strong enough and mentally prepared for a journey that takes at least five hours.
Before the rescue attempt was announced Sunday morning, ambulances were seen zipping up a muddy pathway to take their stations. Several helicopters have been on standby for days, prepared to bring the boys to the hospital.
Officials moved the large media contingent from the rescue site to clear the way for those working directly on the extraction.
Many experts have weighed in on possible extraction methods that would minimize risk to the boys. SpaceX CEO Elon Musk said on Twitter his team was working on a tiny submarine pod that would be ‘‘small enough to get through narrow gaps.’’ It was unclear whether his method would be ready in time or used by Thai officials.
Mental health and medical experts have warned that even if the whole team gets out safely, they are likely to battle weeks, if not months, of mental and physical traumas.
Problems could include depression, anxiety, anger, and an inability to adjust to normal sleep patterns, said Jacob Hyde, an assistant professor of military psychology at the University of Denver who studies reactions to isolated environments.
The group’s camaraderie and Thailand’s cultural context, however, would probably help them after the ordeal, he said.
The assistant coach with the boys, Ekapol Chanthawong, has been using his experience as a novice monk to help the team stay calm through meditation. The names of the boys have not been released.
The coach and the boys have been communicating with their parents through letters, telling their loved ones not to worry and specifying their most pressing food cravings.
‘‘If we can get out, please can you bring me to eat at the pan-fried pork restaurant?’’ one of the boys wrote in a letter published on the Thai navy SEALs’ Facebook page. ‘‘I love you.’’