The rescue mission is under way to save the 12 boys and their coach from inside a Thai cave.
Heavy downpours fell as the mission to rescue 12 boys and their football coach from a Thai cave began. And there's no turning back now.
The boys will be strapped to a diver, given oxygen and told to hold on for dear life and they pass through a flooded cave system that's already claimed one life, with concerns the weather could further hamper rescue efforts.
They boys — cold, malnourished and exhausted — will have to swim large sections of the underground maze and squeeze through tiny gaps, some no bigger than 30cm.
In the latest 11pm (NZ time) update on the progress of the cave rescue operation, the head of the joint command centre, Chiang Rai governor Narongsak Osottanakorn, said it is still unknown how long it might take until the first child has made it out.
"Because of the complexity of the cave and difficulty of the operation, it is unknown how long it will take before the team can bring out the first batch of boys. The divers will work with medics in the cave to assess the boys' health before determining who will come out first," the statement said.
"They cannot decide how many of them will be able to come out for the first operation. 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."
New details of the rescue also emerged, with the boys being divided into four groups, the Bangkok Post is quoting a source as saying.
It says the first group will have four people, with the second, third and fourth containing three people. The coach will be in the final group.
Renewed monsoon downpours have come and gone throughout the past hours, according to reporters at the scene, the Guardian reported.
Rafael Aroush, an Israeli volunteer diver told CNN that speed is "very, very important," now, he said. "(There) might be crucial changes in the rescue operation (plan) and somebody will make a decision maybe to bring more of them out today."
He says because the cave is limestone and there are many streams overflowing into the system, ongoing inclement weather could "destroy the whole operation."
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 dangerous.
"Now the 13, their health and their minds are ready and they all have knowledge of the mission. They're ready to go out," he said. "Today is D-Day."
Thirteen foreign divers and five Thai divers entered the cave system at about 10am (3pm) local time this morning after an Australian doctor gave the all-clear.
The local divers are required because none of the foreigners speak Thai and communication before and during the dive will be key.
The soonest they could possibly be out is about 2am. How quickly they are moved out will depend on the conditions and water levels inside the cave. The boys will be brought out one by one, but operations "may stop and start depending on conditions," Mr Osottanakorn said.
Given the time it will take divers to get each boy out, the operation could take days.
"They can't take them all out at once for fear of a dangerous bottleneck situation," said CNN's Matt Rivers, who is on the scene.
It's understood the hardest part of the mission is a 200m submerged dive. The ABC reports the young boys will be asked to hold on to the divers while they make their way through the cave system.
At one point, they'll be confronted with the narrowest gap in he cave system — a 38cm hole in the rocks they'll have to squeeze through.
For context, a reporter on the scene described the gap as "barely bigger than a standard school ruler or the size of your head".
Water levels inside the cave are fluctuating, making it difficult to know for sure how long some of the dives will take.
The boys will be strapped to their "buddy" by a tether and dragged behind. They will not be carrying gear and the divers will carry two oxygen tanks.
TIME IS RUNNING OUT
CNN's Matt Rivers said the forecast for monsoonal rains meant the situation had become more urgent over the last 24 hours due to oxygen levels dropping inside the cave. While rain has held off within the area, forecasts suggest more could fall.
Mr Rivers noted green netting and barricades had been erected outside the cave entrance and that "it feels different here".
"Journalists are now being forced to leave the area and about a dozen additional ambulances have been brought in. This rescue attempt appears extremely imminent." he tweeted.
ABC news director Gavin Morris also stressed the urgency of the situation amid ominous weather reports.
"The weather has clearly turned . the world is looking on anxiously," he tweeted.
Journalists were asked to leave the site this morning with a new media centre set up 3km away. Thai authorities confirmed the decision was made so that a rescue operation can take place.
It will be a nervous wait until the boys emerge early tomorrow morning. Without a reliable source of communication, the world likely will not know if the operation has been a success until the divers re-emerge.
British, US and Australian divers have reportedly joined the Thai Navy as workers prepare for the rescue attempt. Among them is Adelaide anaesthetist and diving expert Dr Richard Harris.
Osatanakorn said officials are "still at the state of war against the water" and that no plans are perfect.
"All the plans must not have any holes in them," he said, noting that "hundreds of people have vetted this" and "there will always be margins for error."
He said authorities are waiting for two big groups of volunteer divers to arrive later today, after which they'll be ready to begin the operation of bringing them out.
He says: "The plan that I've held on to from the beginning is that we have to bring the kids out and the determining factor of this plan is to have as little water as possible."
He said floodwaters have been drained as much as possible, "but if it rains and adds to it again, we don't know what other risk factors we will have to face."
He also warned about higher carbon dioxide levels in the cave.
- additional reporting news.com.au, Guardian