Pressure is mounting on Thai authorities to bring forward a rescue plan for 12 boys and their coach trapped deep inside a flooded cave in northern Thailand, after the death of a former navy diver and a drop in oxygen levels underground.
Officials initially thought they could keep the boys and their coach in the cave where they are trapped for up to four months, until waters dropped sufficiently for them to be able to walk out.
But the death of a rescue team member, and the realization that oxygen levels have fallen to potentially dangerous levels, appears to have forced a reassessment of the situation.
Thai Navy SEAL chief Rear Adm. Aphakorn Yoo-kongkaew said oxygen levels in the cave had dropped to 15%, a level that one Thai medic said posed a serious risk of hypoxia, the same condition that causes altitude sickness. It was too dangerous to leave the boys much longer, Yoo-kongkaew said, despite the risks involved in attempting to bring them out.
"We can no longer wait for all conditions (to be ready) because of the oppressive situation," he told journalists Friday.
"We originally thought the young boys could stay safe inside the cave for quite a long time but circumstances have changed. We have limited amount of time." He did not say how long they could survive with current oxygen levels, but he said getting more oxygen piped into the boys was top priority.
The SEAL commander spoke just hours after former Sgt. Saman Kunan, an Thai ex-SEAL, died at 2 a.m. Friday (2 p.m. Thursday ET), as he returned from an operation to deliver oxygen tanks to the cave where the boys are located.
The 38-year-old ran out of air while underwater, an official said.
The boys, members of a youth football team, and their coach have been trapped in the labyrinthine cave for nearly two weeks, unable to navigate their way out of a series of narrow passages after floodwaters forced them to take shelter.
'He was a triathlete'
Kunan's death had changed the mood on the ground and made real for rescuers just how dangerous the mission has become.
Volunteer diver Mikko Paasi said that the mood at the camp had changed since the rescue team learned of Kunan's death.
"Definitely you can feel it that it has an effect, but we're moving on. Everyone is a professional so we're trying to put it away and avoid it happening again," said the Finn, who is a long-term resident of Thailand.
"Everybody is focusing on getting these boys out -- keeping them alive or getting them out."
The UK divers who first reached the boys described their dive as "gnarly" and full of tight passages submerged with opaque waters. Authorities have been considering teaching the boys to breathe through scuba oxygen tanks to be pulled out.
One of Kunan's longtime friends, Sgt. Anuram Kaewchano, told CNN he was shocked to learn the news.
"I can't believe this happened," he told CNN by phone. "He was very fit, he exercised every day, and he was a triathlete. Our last trip together was to Malaysia."
He added that the last time the two spoke, "we talked about the kids -- whether they were out yet."
"Diving is always full of risks," SEAL chief Yookongkaew said.
"He may have passed out," causing him to drown, "but we have to wait for the autopsy."
A military aircraft will carry Kunan's body from Chiang Rai to Satthahip Navy Base Friday evening. A funeral service will take place there, and then at his home town in the province of Roi Et, northern Thailand.
Pornphimon Pansurin, a counselor from the nearby Darunrat School who teaches Ekarat Wongsukjan, one of the missing boys, said the missing boys may feel responsible for the tragedy.
"If they learn about what has happened they will blame themselves," she told CNN. "They will feel very guilty."
A huge operation is underway at the Tham Luang Nang Non cave complex, where dozens of Thai Navy SEALs and international experts are attempting to find a way to get the boys out.
The members of the Wild Boar soccer team were reported missing on June 23 when they didn't return from an outing after soccer practice. They entered the cave during fine weather but became trapped when a sudden downpour flooded the narrow tunnels.
The 12 boys and their coach were found deep inside the cave by two British cave divers on Monday, perched on a rock slab above flood waters, after nine days without food or fresh water.
Since then, rescuers have been examining ways to bring the boys out, including fitting them with full-face oxygen masks and accompanying them on a long, dangerous swim through the tunnels.
However, the death of an experienced diver in the cave system underlines the inherent risks in attempting to move the boys, who are physically weak after days without food.
It takes even the most experienced divers up to five hours to swim through jagged, narrow channels from where the boys are to safety outside.
Rescue teams have been pumping millions of liters of water from the cave in an attempt to lower water levels to the extent that the boys can simply walk out.
However more rain is forecast this weekend, putting pressure on rescuers to act soon or have to contend with even higher water levels inside the cramped chambers.
Thailand's monsoon season runs from July to October and, while the past few days have been relatively dry, the long term forecast is rain for months.
The rescue is being further complicated by the lack of oxygen inside the tunnels, as more rescuers enter to carry supplies to the boys, and work to widen tunnels.
Officials said an air hose has been installed to pump more oxygen inside the cave to ensure levels don't fall further. But conditions are hard going -- each dive, through submerged, darkened tunnels, takes dive teams a round trip of 11 hours, from the command center to the boys' cavern.