But with oxygen levels inside dropping to unsafe lows and the prospect of heavy rains flooding the area completely, authorities decided they had to move quickly, and take the group out through the water-filled tunnels.
The eight boys who have left the cave are being treated in an isolation ward in a Chiang Rai hospital. They eventually found a dry landing spot, where they waited for nine days before being found by two British divers.
A retired Thai navy SEAL died Friday after he ran out of oxygen while placing compressed-air tanks along the exit route.
The head of the operation to save a youth soccer team from a cave in Thailand, Narongsak Osottanakorn, said rescuers had learned from experience and were two hours faster in bringing the second batch of survivors out.
"We have more expertise than yesterday", he said.
Staff previously said their first assessments would focus on the boys' breathing and signs of hypothermia, as well as a potentially fatal lung infection known as cave disease.
The boys and their coach first went missing on June 23. It is rainy season in Thailand at the moment, with torrential downpours that appear out of nowhere dominating the weather patterns.
Since it is rainy season, you can expect nearly everyday you will get some type of rain. Reporters near the cave site said heavy rain had been "bucketing down" for hours and that "cave flooding is possible soon".
Torrential rain had not affected conditions for the rescue operation. But then oxygen started running low in the cave, and officials also anxious the little piece of real estate the boys and their coach have could be lost.
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Rescue workers and divers are using the break to rest and prepare for the next phase of the grueling operation, which Osotthanakorn said involves some of the hardest diving in the world. But officials decided "the risk of leaving them there was greater".
Beginning earlier today, the rescue operation has so far been a success with 11 of the 13 now out of the caves and recovering in hospital.
The Associated Press reports that the families of the boys "were being kept at a distance because of fears of infection and the emaciated-looking boys were eating a rice-based porridge because they were still too weak to take regular food, authorities said". Musk said the submarine is expected to arrive in Thailand around 11 p.m. Monday, local time.
Tuesday's operation began just after 10 a.m.
Eight boys were brought out alive over the last couple of days.
Scott and co-producer Adam Smith have reportedly been conducting interviews around the rescue site, where more than 1,000 Thai personnel have been joined by dozens of worldwide specialists for the operation.
Dr. Andrew Adesman, chief of developmental pediatrics at Cohen Children's Medical Center in New Hyde Park, New York, said there is a threat of post-traumatic stress disorder (PTSD) for the boys and their coach, but he said he is hopeful it won't be an issue for a majority of the kids.
And Gianna Infantino, the president of Federation Internationale de Football Association, soccer's governing body, has invited the boys to the World Cup final in Moscow on Sunday. Divers escorted the children, who wore equipment to help them breathe.