SBS News understands that the boys are in a sterile, isolated section of Chiang Rai's provincial hospital.
Reporter Omar Dabbagh said the youngest of the four boys rescued was 11 years old.
"Some of the boys were brought out [to the hospital] in helicopters, some in ambulances," he said.
The front of the hospital has been obscured by a green tarpaulin to prevent media from viewing the rescued boys and hospital staff entering and exiting the building.
The same divers that brought the first group of four boys to freedom will be used to enter the cave again to bring the remaining group out due to their knowledge of the terrain, said Thailand's Interior Minister, Anupong Paochinda.
Emergency workers carry a stretcher with one of the rescued boy to be transported by ambulance. Source: AP
Officials are meeting to discuss the next stage of the complex operation to rescue the remaining eight players and their 25-year-old coach who continue to wait inside the flooded cave.
Chiang Rai's acting Governor Narongsak Osatanakorn said after the first group of boys were successfully rescued, the divers would take a 10 to 20 hour pause in operations so scuba tanks could be replenished with oxygen.
Rain expected to complicate the rescue
It comes after heavy rain fell overnight with grey skies greeting rescuers when they woke up on Monday morning to continue efforts to bring the team to safety.
Meteorologists say there is a 60 per cent chance of further rain on Monday.
Cheers of joy and applause greeted four boys when they emerged from the cave on Sunday evening with their accompanying eight divers.
The first four boys are rushed to hospital after their ordeal. Source: EPA
Rescue went 'better than expected'
The rescue operation has attracted worldwide attention and involved expert cave divers from countries including the US, Australia, UK and China.
The boys, many of whom are not confident swimmers, have been given training in scuba diving so they can navigate the flooded passageways, with one measuring just 38cm in diameter.
"The operation went much better than expected," Osatanakorn, the leader of the rescue mission, said on Sunday night.
Richard Harris has been assisting Thai rescue workers at the scene. Source: diveoztek.com.au/Richard-Harris
Elon Musk tests mini-sub to assist rescue team
The news comes as Elon Musk's Space X rocket company continues to test a "tiny kid-sized submarine" that it believes will be able to help free the children.
The mini-sub was being tested in California and, if successful, it will be flown on a 17-hour flight to Thailand, a spokesman for Musk's Boring Co. said, adding that Thai officials had requested the device.
A video of the testing has been posted on Twitter.
Eight of the Thai boys are now out of the cave. Source: AAP
Australian divers involved in rescue
Six Australian Federal Police divers are supporting the Thai Navy in the mission, together with a liaison officer and interpreter.
The divers formed part of the 'daisy chain' of rescuers who led the four boys to the surface on Sunday.
A South Australian anaesthetist and experienced diver Richard Harris was part of the medical team that determined the boys' fitness to undertake the arduous four kilometre journey.
The death Friday of a former Thai navy SEAL, Saman Gunan, underscored the risks to divers on the rescue team.
The diver, the first fatality of the rescue effort, was working in a volunteer capacity and died on a mission to place oxygen canisters along the route.
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