The rescue mission began on Sunday morning, almost a week since the 12 boys, aged 11-16, and their coach had been discovered on an embankment 2.5 miles (4 kilometers) inside the winding tunnels.
Four more of the boys were carried on stretchers out of the labyrinthine Tham Luang cave on the Myanmar border at dusk on Monday, bringing to eight the number brought out after two rescue pushes on successive days.
Chiang Rai Gov. Narongsak Osatanakorn says the rescue mission began at 10.08am and involves 19 divers. It took the divers about eight hours to get into the cave, reach the boys and bring them back out.
Tuesday's rescue mission will be a race against time and bad weather.
It has emerged the rescued boys are being held in confinement over fears they have cave disease, which is caused by breathing in fungus from bat and bird droppings.
The boys, who play for the Wild Boars, are likely be kept in hospital for a week to undergo tests, officials said.
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They have real enthusiasm for these players, not only for the way they have played but also for the way they have conducted themselves.
Torrential rain struck the cave site on Monday evening and the downpour continued through Tuesday morning, but authorities said preparations for the final rescue mission were unaffected.
They are all likely to stay in hospital for seven days due to their weakened immune systems.
Dr Richard Harris and his dive partner Craig Challen have issued a statement thanking people for their support and words of encouragement after the successful cave dive rescue of 12 trapped boys and their football coach. Lit by several beams of white light, the divers in wet suits and helmets are seen submerging themselves in the water and grabbing on to a metal dive line used to guide them through the winding channels of the six-mile cave.
Doctors are taking no chances with their physical recovery, quarantining the group, administering tetanus and rabies shots, and putting two of the team on antibiotics after they showed signs of pneumonia.
"We had a little bit of hope that they might still be alive but we had to do it, we just had to move forward", Rear Adm Arpakorn Yuukongkaew said.
The Wild Boars soccer team and their coach are expected to spend a week in hospital.
Elon Musk, the billionaire owner of Tesla and SpaceX, was in Thailand with engineers from his companies to offer their expertise in the rescue.