Ambulances have been moved and preparations made Monday to rescue the second batch of boys from the flooded Luang Khun Nam Nang Non cave.
But the efforts to rescue the boys - aged between 11 and 16 - have proved a monumental challenge.
Thailand's Prime Minister Prayut Chan-o-cha was due to arrive at the site Monday to oversee the remainder of the operation, according to government spokesman Lt. Gen. Sansern Kaewkumnerd.
Reuters could not confirm the identity of the two people brought out in the evening and the chief of the rescue mission, Narongsak Osottanakorn, asked about the two, declined to comment, saying a news conference would be held soon.
Four more members of a youth soccer team were pulled from a flooded cave in a second round of rescue operations in Thailand on Monday.
Narongsak said after the first four boys were rescued that they would be quarantined "for a while because we are concerned about infections".
It took hours to place oxygen tanks and guide ropes along the narrow tunnel leading to the boys. Relatives were able to see them through a glass partition, the governor said. Four boys and their football coach are still trapped inside the cave.
They wore full-faced masks "while hanging on to the bodies of rescue divers", Channel News Asia reported.
Then came the letters carried out by the teams of divers who took oxygen, food and medicine to the boys' refuge as experts pondered whether to dive them out or provision them for months while the monsoon season continues until at least late October.
Thirteen divers and five Thai Navy SEALs are involved in the operation, in which the trapped team must walk or wade through muddy areas of the winding cave and rising waters.
The Thai official leading the rescue operation, which has involved two elite British divers, said it has gone "better than expected" and that the healthiest boys have been taken out first.
In an indication of how unsafe the journey can be, a former Thai navy diver died in the caves on Friday.
A Royal Thai Police helicopter carrying rescued schoolboys lands at a military airport in the northern province of Chiang Rai, Thailand, July 8, 2018. "From what I've seen in the clip, they did look skinny", he said.
Narongsak defended the lack of public disclosure of the names of the boys who had already been guided to safety, saying it "will create ill feeling" if their names are released while others languish inside the cave.
A total of eight boys have now been rescued.
The remaining nine boys are still at the location where divers had found them about 500 metres from the so-called Pattaya Beach.
He told reporters the four rescued boys were taken to the hospital in the town of Chiang Rai, the provincial capital, for evaluation, and the next phase of the operation will resume after about 10-20 hours.
A green tarpaulin is used to cover the entrance of the Chiangrai Prachanukroh Hospital, where the four rescued boys are being kept in quarantine.
Authorities have repeatedly said the rain could re-flood crucial parts of the cave complex that have been drained and make the escape route much harder or even impossible to navigate.