Finnish volunteer diver Mikko Paasi, a long-term resident of Thailand, said the death of the Thai Navy SEAL had changed the mood on the ground and made real for rescuers just how unsafe the mission had become. They are now at the field hospital near the cave, Reuters reports.
The operation began at 10 a.m.
Just after 9 p.m., Thai navy SEALs posted on their Facebook page again, saying: "Have sweet dreams everyone".
It was unclear who was inside the ambulances or the helicopter.
"Today is D-Day", Narongsak Osottanakorn, head of the rescue mission, had earlier told reporters.
The soccer team disappeared on June 23 and were later found stranded in a small chamber of the flooded Tham Luang cave complex, capturing the world's attention and fascination. The team and coach were exploring the cave after a practice game when heavy rainfall and flooding cut off their escape route out of the cave and prevented rescuers from finding them for nearly 10 days.
A second group made up of the others had also begun the journey from the chamber where they had been trapped, a rescue worker told AFP.
Given the risk of the oncoming rains that could undo the drainage efforts, Mr Narongsak said the conditions were now ripe for the boys to be evacuated.
For the boys, the most unsafe part of the journey out of the labyrinth cave system remains the first kilometer, in which they are required to pass through a flooded channel no wider than a person. "Based on the complexity and difficulty of the cave environment it is unknown how long it might take and how many children would exit the cave".
It has previously taken divers 11 hours to complete the round trip. "I promise to take the very best care of the kids", he said in a note given to divers on Friday, July 6.
An "all-star" team of 18 divers entered the caves this afternoon as the boys and their families were notified of the development.
Expert divers worked together to rescue guide the boys out through the narrow passageways of the cave.
According to Maj. Gen. Chalongchai Chaiyakam, the 13 "will continuously come out in approximately 2-4 days, which all may change depending on weather and water conditions". Once the team are ready, they will do so immediately.
Mental health and medical experts have warned that even if the whole team gets out safely, they are likely to battle weeks, if not months, of mental and physical traumas.
Narongsak says the rescue mission was launched because floodwaters inside the cave are at their most optimal level.
"If we wait and the rain comes in the next few days we will be exhausted again from pumping and our readiness would drop".
"To all the kids", wrote a mother of one of the boys, "we are not mad at you at all".
News says two members of the youth soccer team trapped for two weeks in a Thailand cave have been rescued by divers.
Another official involved in the rescue operation said the initial six who had been saved formed a first group. The boys will gradually come out accompanied by two divers each.
The only way to bring them out of Tham Luang Nang Non in Chiang Rai province is by navigating dark and tight passageways filled with muddy water and strong currents, as well as oxygen-depleted air.
Officials have said that conditions are as flawless as they can be for the rescue attempt, factoring in the weather and water and oxygen levels in the cave, as well as the boys' health.
The governor has called the rescue a "war with water and time".