A former Navy Seal has died trying to help rescue 12 boys and their coach who have been trapped in a cave for nearly two weeks.
Saman Kunan died due to a lack of oxygen in the tunnel, according to Commander Arpakorn Yookongkaew.
It has been reported that Mr Kunan was trying to reach a cavern set up as a command centre 1.2 miles inside the underground system when he ran out of air.
He had been working in a volunteer capacity and was returning to the centre after placing oxygen tanks through the cave's underground network.
A diving partner tried to revive Kunan but was unsuccessful.
Maintaining air supplies inside the cave has become the 'top priority' as rescuers face the prospect of the boys remaining underground throughout the monsoon season, which ends in October.
Oxygen in the chamber is now down to 15% according to The Guardian and normal oxygen levels are at around 21%.
Deputy army commander, Chalongchai Chaiyakham, said he was unsure how long the boys could survive in such conditions.
A huge operation is underway at the Tham Luang Nang Non cave complex, in Chiang Rai, northern Thailand.
Dozens of Thai Navy Seals and international experts are attempting to find a way to get the boys out.
Rescuers have been analysing ways to rescue the boys, including fitting them with full-face oxygen masks and accompanying them on a long, dangerous swim through the tunnels.
However, the death of Mr Kunan, who was an experienced diver, highlights the inherent risks in attempting to move the boys - who are physically weak after days without food.
According to a doctor's report, two boys and the coach are suffering with exhaustion through malnutrition.
Now a team of bird's nest collectors from southern Thailand have arrived to put their rock climbing skills to use in a bid to help with the rescue mission.
The eight men climb limestone cliffs to collect the edible nests - a delicacy made from solidified bird spit that can sell for hundreds of pounds per kilo.
The group's leader, 49-year-old Abdulrawheep Khunraksa said: "One member in our team was watching (the rescue mission) on television and thought 'how can we help them?'
"We thought that we might have the expertise to help since we have climbed to collect bird's nests for generations."
The team will now set off up the steep slope in the hopes of finding an alternative route to reach the boys inside the Tham Laung cave.
Featured Image Credit: PA