Officials said Saturday they were aiming to rescue the boys before seasonal monsoon rains hit, which could flood the caves. Officials had said earlier that helicopters were on standby to take anyone rescued from Tham Luang Nang Non cave in Chiang Rai province to a hospital.
Media have been asked to leave the area by 9am local time (noon, AEST) Sunday, and the site was evacuated for a "rescue operation".
Four of the 12 Thai schoolboys were rescued from a flooded cave on July 8 as divers launched a daring and risky mission to free the children and their soccer coach who have been trapped underground for more than two weeks, officials said.
Speaking at a press conference on Sunday morning local time, Chiang Rai acting Governor Narongsak Osatanakorn said the trapped boys were aware of efforts being made to rescue them but the extraction will be long and incredibly unsafe.
The rescue operation will now pause for at least 10 hours, according to Narongsak Osatanakorn, chief of the command centers coordinating the rescue, so that divers can replenish their oxygen tanks.
A total of 18 expert divers - 13 global and five Thai - were proceeding deep into the hillside through the waterlogged passages to the chamber where the team is located. The path out is considered especially complicated because of twists and turns in narrow flooded passages.
Maj. Gen. Chalongchai Chaiyakam said the 13 "will continuously come out in approximately two to four days, which all may change depending on weather and water conditions", The Associated Press earlier reported.
"From the situation assessment, we need to use the area to help victims".
The boys, aged between 11 and 16, went missing with the 25-year-old after soccer practice on June 23 after they set out to explore the Tham Luang cave complex in a forest park near by the border with Myanmar. Monsoon flooding cut off their escape and prevented rescuers from finding them for nearly 10 days, CBS News reported.
They were discovered by British divers on Monday night after a nine-day round-the-clock search involving teams from all over the world. It was not immediately known if a US diver was among them.
On Friday, officials warned that oxygen levels in the cave dropped from 21% to 15%, complicating rescue efforts.
It is also worth mentioning here that most of the boys are unable to swim with no diving experience.
They are apparently safe and reasonably well.