While the names of those rescued have not been released, six of the boys are students at the Maesaiprasitsart School and classmates say they've been closely monitoring the worldwide mission to save them.
Typically people would learn to scuba dive before embarking on a more technically challenging cave dive like the one involved in the rescue effort, said Chris Foisey, a St. Catharines, Ont. -based scuba instructor with experience diving through underwater tunnels.
The good news today, he said, was that the rescue team spent nine hours - two hours faster than they did a day earlier - from the time they went deeper into the cave to extract the four survivors until they emerged safely from the cave.
The footballers still awaiting rescue are about two kilometers further in, at a point very hard to access.
Four boys were successfully rescued on Sunday during a gruelling eight-hour rescue operation.
Classmates react after a teacher announces that some of the 12 schoolboys who were trapped inside a flooded cave, have been rescued, at Mae Sai Prasitsart school, in the northern province of Chiang Rai, Thailand, July 9, 2018.
Operations kicked off at about 5am BST (11am Thai time) when a team of 18 elite Thai and global divers entered the cave. "The plan that I've held on to from the beginning is that we have to bring the kids out and the determining factor of this plan is to have as little water as possible", Chiang Rai acting Gov. Narongsak Osatanakorn said, adding that floodwaters have been drained as much as possible.More news: We're easy to analyse but tough to beat, warns Sweden coach
Two more boys left the Tham Luang Nang Non cave complex a short time later and were transferred to a medical facility on site, followed soon after by a fourth boy, according to the eyewitness, who is stationed at the entrance to the cave. Seven Britons chaperoned the boys through the treacherous tunnels as part of a team that included 18 global cave divers and five elite Thai navy SEALS.
None of the rescued boys' identities have been revealed.
'A flash flood because of sudden heavy rain locked them in'.
"We have more expertise than yesterday", he said.
The rescued boys will be in quarantine for at least 24 hours, Tracy reports.
Ultimately, however, there are so many unknowns, and it's hard to predict what pathogens, if any, the boys have been exposed to, Adalja said. "If we bring five we have to change the plan". He had placed oxygen tanks along the route but didn't have enough air to get back to safety.
The death of military diver Saman Kunan on Friday underscored the huge risks the boys face.