Rescuers are racing against the rains to free 12 boys and their football coach, who are trapped in a flooded cave in northern Thailand.
A deluge is expected to hit in a matter of days that could force the water level up, threatening to flood the pocket where the group took refuge.
The teenage boys and their 25-year-old coach have been trapped for 12 days.
They were found on Monday night by rescue divers, on a rock shelf about 4km (2.5 miles) from the cave mouth.
The boys have now received food, foil blankets, and medical attention, and rescuers are trying to run cables through the cave tunnel so they can speak to their families.
When are the rains coming?
The region of Chiang Rai where the boys are trapped has for the past few days experienced a dry spell, and rescuers have taken advantage of this to pump water out of the cave complex.
About 128 million litres of water had been pumped out by Thursday, with the water levels coming down at an average rate of 1.5cm per hour. Rescue workers are now able to walk through a 1.5km (0.9 mile) stretch from the entrance to what's being called the third chamber.
But heavy monsoon rains are forecast for Sunday. Chiang Rai Governor Narongsak Osotthanakorn said they were "racing against water".
"We are calculating how much time we have it if rains, how many hours and days," he said.
The Tham Luang cave complex is regularly flooded during the rainy season until September or October, raising fears that a delay could leave the boys trapped in the cave for months.
What is being done to rescue the boys?
There is hope that enough water can be pumped out of the cave tunnels for the boys to be able to wade - or be floated - out.
But rescuers are also planning for other eventualities.
A team are exploring the forested mountain land above the cave complex to see if they can find a chimney down to the cavern sheltering the boys. They have enlisted the help of bird-watchers, who are specialists in finding hidden holes, the AFP news agency reports.