The Thai boys trapped in a cave are running out of oxygen

The mission to rescue 12 boys and their coach trapped deep in a Thai cave took a dark turn Friday, with a rescuer dying in the complex, and plummeting oxygen levels making it dangerous for the group to remain underground much longer.

The developments have placed a new urgency on getting the group out of the cave complex, where they have been trapped in a chamber about four kilometers from the entrance for 13 days.

Thai authorities had initially thought, in a worst-case scenario, they could potentially sustain the group with food and medical supplies for up to four months if no other way to free them was found before water levels naturally receded.

But the dropping oxygen levels in the complex have ruled out that possibility. Rear Adm. Aphakorn Yoo-kongkaew, Thailand’s Navy SEAL chief, told reporters Friday that oxygen had dropped from a normal level of 21 percent to 15 percent, making it dangerous to leave the boys much longer.

"We can no longer wait for all conditions because of the oppressive situation," he said.

"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."

The hazards of the cave complex, a network of dark, flooded tunnels that take specialist divers more than five hours to navigate each way, was underlined when one of the rescue team died early Friday.

Saman Kunan, a former Thai Navy SEAL, died at 2 a.m. when he ran out of oxygen on his way back from delivering oxygen tanks along the route out, officials said.

Yoo-kongkaew said the 38-year-old, who is being hailed as a hero for his efforts, appeared to have passed out, causing him to drown.

The operation to free the boys, aged 11 to 16, and their 25-year-old soccer coach, has taken on huge proportions, drawing experts and volunteers from across the world. Tesla’s Elon Musk said Friday that engineers from his companies were en route to Thailand to see if they could help.

With heavy monsoon rains forecast to hit the region this weekend, rescuers are in a race against time as they face the twin threats of rising waters, and dropping oxygen levels. Narongsak Osatanakorn, the governor of Chiang Rai province where the cave is located, told reporters that the presence of hundreds of rescue workers inside the cave was depleting oxygen levels in the complex.

The rescue teams are working on multiple fronts. Using hundreds of industrial pumps, they have drained than 130 million litres of water from the complex this week, in hopes of clearing flooded stretches and potentially allowing the group to wade out.

Experts stationed with the group, who are severely weakened and traumatized by their ordeal, have been sustaining them with food and medical supplies, while attempting to teach them the basics of scuba diving in case that is the only option to escape the cave. The route out features narrow, flooded passages that would require the boys to dive alone, with guidance from Navy SEALS.

Meanwhile, teams of scouts have been combing the forest area an estimated 800-1000 meters above the chamber where the group is trapped, searching for any vents where they could potentially drill to reach the boys. At a press conference late Friday, authorities said they had only found dead ends, but would continue their efforts Saturday.

The group was found by a search team deep inside the cave complex Monday, after nine days underground with no food. The young soccer team, nicknamed the “Wild Boars,” had been missing, feared dead, since a trip to explore the cave after a practice session on June 23.