MAE SAI, Thailand — When the wail of the ambulance siren first reached the Thai village, people started cheering: The sound meant one of the boys trapped in a cave for more than two weeks was out at last and on his way to the hospital.
After more than a week of searching the flooded cave complex, and then days of planning a daring and increasingly desperate rescue, divers safely evacuated four of 13 members of a youth soccer team on Sunday.
Nine remained behind, waiting their turn to escape, as of early Monday morning. The boys on the team range in age from 11 to 16, and the coach with them is 25.
One by one, the first four to be rescued emerged after a treacherous, hourslong journey through the tight, underwater passageways of Tham Luang Cave. Skilled cave divers, part of a team assembled from around the world, hugged the four to their bodies as they swam through the dark.
“The 4th wild boar is out of the cave,” said a posting Sunday evening on the Facebook page of the Thai Navy SEALs, who are aiding in the rescue. The Wild Boars is the name of the boys’ soccer team.
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After the first four were rescued, however, the evacuation came to a halt. There was no choice: The rescuers had used up all the air tanks divers had placed along the route, said Narongsak Osottanakorn, the head of the search operations. It would take divers 10 to 20 hours to replace the tanks for the next rescue attempt, he said.
The rescue was far from over — but it was a remarkable turn in the 16-day drama that has captivated Thailand and the world.
“Today, everything was very smooth,” Mr. Narongsak told a throng of reporters at a news conference. “Today is the best day, with the best situation of the weather, the health of the boys and the water level.”
It took 10 days just to locate the missing boys, who were deep inside the flooded cave complex. Then it took nearly another week to figure out a way extract them.
None of the options were easy: Drill through a mountain. Wait months for the floodwaters to recede. Or escort scared and exhausted young people, few if any of whom could swim, through an underwater maze that was daunting even for the world’s best cave divers.
After considering several alternatives, Thai officials settled on a tandem dive arrangement with the boys wearing full face masks so they could breathe normally.
Underscoring just how dangerous getting the boys out of the cave could be, the operation suffered its biggest setback on Friday, when a volunteer diver, Saman Gunan, 38, a former Thai Navy SEAL, died after losing consciousness while underwater. He had been placing air tanks along the route — the same task that other divers must now hurry to complete.
But Sunday’s rescues went more quickly than expected, offering hope that the remaining nine team members could be extracted soon and safely.
With most of the team still in the cave, the rescuers were racing against time, and the weather. Dark clouds shrouded the mountains above the cave much of the day Sunday, bringing heavy rains and threatening to raise the water level in the cave once again.
Mr. Narongsak said 90 divers assisted in Sunday’s rescue, about 50 of them from overseas. He said 18 divers — 13 foreigners and five Thais — made up the team that brought out the four.
He did not say which countries the foreign divers came from, but British cave divers have played a key role in the operation, and the United States, Australia and China have all sent teams to help. Divers from several other countries have also volunteered.
The divers entered the cave at 10 a.m., and Mr. Narongsak said at the time that he expected the first rescue to be done by 9 p.m. In fact, it was three hours earlier than that. The last of the four was taken from the cave before 8 p.m.
All four were quickly transported to a hospital in Chiang Rai, the nearest large city.
Before the mission began, expert divers said the first mile of the journey out of Tham Luang Cave would be the most dangerous.
The tandem divers could expect to face strong currents and pass through perilous tunnels, without any air pockets for safety in an emergency.
“Everyone knows exactly what they have to do, because any confusion in there would be really bad,” Mr. Narongsak told reporters shortly after the operation began.
Only a day earlier, on Saturday, Mr. Narongsak had told reporters that a rescue attempt was not imminent. But the weather worsened suddenly overnight, prompting officials to move quickly.
“We believe there are no days when we have been readier than today,” Mr. Narongsak said on Sunday. “If we don’t do the rescue on the day when we are readiest, we might lose the opportunity to carry out this mission.”
The cavern where the group took refuge is about 2.5 to three miles from the cave’s lone entrance. When the cave is flooded, it can take skilled divers more than five hours to make the trip from the entrance to the cavern.
Crews have been pumping huge amounts of water out of the cave, which has helped improve access to the area. But water levels farther from the entrance have dropped more slowly.
Residents of the region were jubilant over the rescue of the first four.
In the town of Mae Sai, where the trapped boys’ soccer team is based, residents and family members celebrated the sound of every helicopter and ambulance they heard, proof that some boys had left the cave and were being rushed for treatment. The medical conditions of the four people rescued were not known.
“I am so happy!” said Kamon Chanthapun, an adviser to the boys’ team. “I was so worried because they are just children, stuck for so long in the dark.”
One of the team members, Adul Sam-on, is a student at the Ban Wiang Phan school here. Inside, students had written messages on heart-shaped sticky notes placed in a big heart shape on a bulletin board with optimistic messages. “Hopefully our friend can come out safely,” read one.
Adul was the boy who spoke to British divers in English in the video that announced to the world that the team had finally been found after 10 days stuck in the cave.
Many family members have spent every day and night at the command center near the cave, praying for the boys to come out alive.
Relatives said they were not angry with the coach, Ekkapol Chantawong, for taking the boys into the cave. Instead, they praised his efforts to keep them alive during the ordeal.
“He loves the children,” said Nopparat Khanthawong, the team’s head coach. “He would do anything for them.”
The boys’ got trapped in the cave on June 23 after they biked there with Mr. Ekkapol after practice.
The vast cave complex was mostly dry when they entered. But the cave is, in essence, a seasonal underground river, and rain began falling soon after they arrived. Within hours, they were trapped by rising water.
Their discovery after 10 days inside the cave, and the successful evacuations on Sunday, beat what many had seen as discouraging odds.
A United States Air Force rescue specialist and cave diver who is assisting in the operation said conditions in the cave complex were so challenging that finding the boys was akin to climbing Mt. Everest. And bringing them all out safely, officials said, would be even harder than locating them.
Two British divers discovered the group on Monday evening just as they were laying down the last of their guidelines and were about to turn back.
Since then, the boys have been regaining their strength and learning how to use diving gear in preparation for their escape.
Four Thai Navy SEALs have stayed with the group, including a Thai army doctor who is also a SEAL, who was seen on a video clip treating their scrapes and cuts.
In Thailand, the plight of the boys brought together, at least temporarily, a country that has long been divided between the urban elite and the rural poor.
The country also has a relatively new monarch, King Maha Vajiralongkorn Bodindradebayavarangkun, who ascended the throne in 2016. He has let it be known he is closely monitoring the search and rescue operation. He donated supplies to the rescue effort and urged officials to bring out the boys as soon as possible.
On Monday, divers are expected to try to rescue as many of the remaining boys as they can.
“I’m really happy now,” said Mr. Nopparat, the head coach. “But I’m still rooting for the rest of the team.”