Specialist cave divers scrambling to rescue a group of villagers trapped in a flooded cave in a remote part of Laos are cautiously optimistic that they may be able to start bringing out the stranded men soon.
Five of the seven missing villagers were located on Wednesday in a chamber deep underground in Xaisomboun, a central province of the landlocked South east Asian nation, a week after they became trapped when heavy rain triggered flash flooding, blocking their way out.
A Laotian rescue group, Rescue Volunteer for People, said that five of the men found were "alive and all safe."
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One of the men, named Mued from a village called Ban Pha Yai, praised officials and his relatives following his rescue.
"I'd like to thank everyone all my relatives, brothers and sisters," he told CNN.
"Thank you very much to the district and provincial authorities, and everyone who came to help."
Rescuers believe two men remain missing somewhere inside the cave complex.
Video released by the rescue group captured the moment divers reached the trapped villagers after emerging from the water.
The men could be seen sitting on a rocky ledge surrounded by floodwater and wearing headlamps.
Rescue teams working above ground were seen jumping for joy, hugging one another and crying when they learned that five people had been found alive, in scenes posted on social media.
For now, they remain stuck in an underground cavern, as rescuers continue to search for the two remaining people, and simultaneously formulate a plan to extract the survivors.
Echoes of Thai cave boys
The harrowing mission to retrieve the trapped men recalls the dramatic 2018 rescue of teenage soccer players in neighbouring Thailand.
Some of the international members on the current mission are themselves veterans of that operation.
"Five people have been found alive and are safe. They have already received basic medical checks and soft food following doctors' advice," Thai rescue diver Kengkard Bongkawong wrote on Facebook at 11.30pm (local time).
"If access can be opened further, rescuers believe the survivors are physically strong enough to help move themselves out with support from the teams."
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Finnish diver Mikko Paasi, who is part of the rescue operation, expressed his happiness at locating five of the trapped.
"The task so far has been far from easy and everybody involved has done amazing work," he wrote on Instagram.
However, he added it was "only a brief relief," as the survivors are still stuck in the cavern for now.
"All healthy and in good spirits, but the extraction is still ahead and it ain't going to be easy," he said.
Video footage taken by Paasi shows the villagers being asked for their names and whether they were suffering from any illnesses.
They responded that they are not ill but feel weak and very hungry.
Challenges ahead
Extraction will likely prove challenging.
Some areas of the pitch-black and partially flooded tunnel appear very narrow, with a width of roughly 58cm.
One of the rescuers said he was at one point forced to remove his equipment in order to squeeze through and reach the next area of the cave.
The villagers, who are understood to all be male, went into the cave last Wednesday in search of gold, but heavy rain triggered flash flooding which blocked the exit, Kengkard said.
The dangerous operation to rescue them was launched amid deteriorating conditions and unforeseen delays, including rescuers encountering toxic hydrogen sulfide gas and issues deploying a pump into the cave to supply fresh air.
Speaking to CNN on Thursday, Kengkard said the men are about 200 metres inside the cave system, which has several chambers and elevated ledges.
To reach them, rescuers need to navigate bends and crawl through narrow passages at different angles.
"Right now, going in and out each trip takes about an hour because oxygen levels are limited," he said.
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Complicating matters, the route is one-way and includes sections submerged in water, which means rescuers must keep in constant communication so as not to cross paths.
"Finding them was never enough. I immediately started planning how to transport them out afterward," Kengkard said.
Their best option now, he added, is to push ahead with pumping as much water as possible out of the cave to lower the water levels and allow the survivors to crawl out themselves.
But to complete the rescue, the team requires more oxygen and specially designed stretchers that can be used in the cramped, narrow caves.
"If the survivors become weak, dragging them alone won't work," Kengkard said.
"We also urgently need more oxygen tanks, 40-litre tanks, to place along the route because the air inside is insufficient."
To help speed up the rescue, teams are pumping water out from several downstream points, and searching for vertical shafts that could allow rescuers to descend directly toward the group, he added.
Rescue Volunteer for People, the Laos rescue group, said they are excavating an access route to the remote cave site so they can move a generator close to the cave's entrance and pump more water out faster.
If they succeed, the group's president Bounkham Luanglath, said the five survivors would be able to get out of the cave "without needing to dive out themselves, because it would be extremely difficult for them to do so."
Hindering their work has been "constant rain" and a four-kilometre trek through difficult terrain.
"We hope they will be able to exit naturally through the same passage they entered from," Bounkham said.
Efforts are also underway to locate the remaining two missing people and get more information about who they are.
They aren't known to the five survivors, and rescuers believe the two entered the cave earlier than the group found on Wednesday.
Rescuers earlier told CNN that more than 100 people had joined the operation, including 15 experienced divers and experts who helped in the dramatic 2018 cave rescue of a young soccer team in Thailand.
