July 8 (UPI) -- Four boys were rescued Sunday night after 16 days in a cave in Thailand, and eight other youths and their soccer coach will attempt the journey out after a break of about 10 to 20 hours.
The rescue will resume after authorities assess conditions in the cave, get a briefing on the initial rescues and replenish the oxygen tanks, Chiang Rai provincial Gov. Narongsak Osatanakorn said at a press conference.
The first two boys -- described as the weakest of the group -- emerged from the Tham Luang cave complex and were immediately transported by ambulance to Chiang Rai Prachanukroh Hospital one hour away. Divers had entered the cave nine hours earlier to begin the rescue efforts.
A short time later, the Thai Navy SEAL official Facebook page announced four people were out of the cave.
The boys were rescued using full face masks, Narongsak said at a news conference where he described it as the "very smooth operation."
The boys' conditions were "not that bad" and "they're OK," according to Eve Tapanya from the Tourist Police.
With oxygen levels dropping to 30 percent and approaching monsoon rains, authorities decided now was the time to rescue the boys aged 11 to 16, Narongsak said at an earlier news conference.
In all, 13 foreign divers and five Thai SEALS are involved in the rescue, which requires a treacherous, 2.4-mile journey through the cave complex.
They expected the process to take two or three days with two divers escorting each boy.
"We have a fraction of a second to help them come out," the governor said.
At 10 a.m. local time, 10 divers headed to chamber 9 where the boys are located and the others will remain along the route to assist.
"They insist they are ready to come out," Narongsak said Sunday of the rescue team. "Family has already been notified."
He added doctors assessed they were "very fit physically and mentally ... They are determined and focused." The group and their families agreed that they should be moved as soon as possible, he said.
The trip entails foot walking through muddy areas or floating through water.
"There are two obstacles, which are water and time," Narongsak said. "We have tried all possible ways to get the boys out, but sometimes we can't win over nature."
Ruled out was drilling into the cave from above.
"Experts' assessments indicate that today is the most ready we can be," Choorat Panngao, Provincial Police Region 5 deputy commander said. "If we don't do it today we will lose our opportunity."
Narongsak said efforts to remove floodwater and divert water flows have been "very successful," but seasonal monsoon rains are forecast to hit the region this weekend and throughout next week.
"We are very happy with the water situation here," he said. "The perfect situation would be to have zero water, which is impossible. The water level would be zero during December or January, so this situation is absolutely impossible. The next best situation would be if the water level is as low as possible to move the kids."