Rescued schoolboys are moved from a military helicopter to an awaiting ambulance at a military airport in Chiang Rai, Thailand, July 9, 2018.
Thai officials started the rescue operation on Sunday as weather experts predicted more rain in the coming weeks.
The eight boys already evacuated from the cave over the weekend are being held in isolation - and aren't even allowed to hug their parents - as doctors assess them for histoplasmosis and other conditions.
"(They) will be extracted today", rescue chief Narongsak Osottanakorn told reporters, adding the journey out should be faster than on previous days.
Rescue leader Narongsak Osatanakorn said at a sudden press conference on Tuesday that the mission began at 10.08 a.m. local time and that everyone in the cave is expected to be rescued today. Rescue officials said the team's coach, Ekkapol Chantawong, who also remains stranded, was among "the weakest in the group" because he gave up his share of food and water to the children in the early days of their entrapment. He was taken by helicopter and then ambulance to the hospital in Chiang Rai were the first four boys, who were rescued on Sunday, are now being held in quarantine as they undergo tests.
One of the boys appeared to have lung inflammation, and another was admitted with a slowed heart rate but both are improving, said Dr. Jedsada Chokedamrongsook, the permanent secretary of the Thai Health Ministry.
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.
However the boys - aged between 12 and 16 - would remain in quarantine until doctors were sure they had not contracted any infections from inside the cave.
"The kids are footballers so they have high immune systems", he added. Dr Jesada said the first group taken out, on Sunday, were aged 14 to 16 and the second group, taken out on Monday, were aged 12 to 14. It was 10 days before the boys were miraculously located, and the remaining five have been in the cave for eight days.
Operations to pump water out of the cave went on despite heavy rain showers on Sunday and Monday.
On Monday, rescuers retrieved four more boys, bringing the total freed so far to eight. The first and longest mission took 11 hours.
The four rescued boys have been transported to a Chiang Rai hospital for treatment and medical evaluations, reported CBS. Crowds at the teeming rescue site cheer the good news, but attention soon turns to the hard task of getting the boys out safely.
Two boys and their 25-year-old coach remain in the cave.
Tech billionaire Elon Musk has also been lending a helping hand to the rescue effort.
"Just returned from Cave 3", tweeted the CEO. They were trapped in the Tham Luan Nang Non cave that became flooded by monsoon rains while they were exploring it after a soccer practice on June 23.