Leaders of the rescue effort at Tham Luang cave in Chiang Rai are considering whether it will be practical to bring out the 12 trapped young footballers and their coach from the flooded cave over the next few days.
It would be "favourable" to stage an evacuation before fresh rain and a possible rise in carbon dioxide sets in, according to former Chiang Rai governor Narongsak Osotthanakorn who has been put in charge of the rescue operation.
"Now, water in the cave is down to satisfactory levels and the weather is fine. The boys' health has begun to improve and they have now learned the basics of diving," said Mr Narongsak, who is now Phayao governor.
"In the next two or three days, the conditions may be perfect to carry out the rescue plan,'' he told reporters yesterday afternoon.
The main concern is now the level of oxygen in the cave, Mr Narongsak said, adding that more clean air has been fed into the cave and more oxygen tanks have been brought in.
The number of rescuers operating in the cave complex will now be kept to a minimum to preserve oxygen and prevent a possible increase in carbon dioxide, Mr Narongsak said.
However, at least four rescuers will be sent in to look after the 12 boys and their coach who are sheltering on the ledge called Nern Nom Sao, he said.
Mr Narongsak added that two more British cave diving experts have arrived in Chiang Rai to support the rescue bid and another two from Britain will come today.
Citing estimates from cave divers and experts, he said that if there are more heavy downpours, the water level may rise to the area where the children are sitting reducing their livable space to less than ten square metres.
Mr Narongsak also said that officials from the Natural Park, Wildlife and Plant Conservation Department, army soldiers and birds' nest collectors from Trang were combing the hill for ceiling crevices that might lead down into the location where the football team is sheltering.
According to CNN, officials are considering a rescue plan involving a "buddy dive", where an experienced adult diver would swim with each boy, according to a US official familiar with the joint rescue operation.
Thai divers would lead the mission and US divers would preposition oxygen tanks, the US official said. The rescue team also includes divers and workers from Australia, the United Kingdom, and other parts of Europe and Asia.
Thai military officials have been briefed, the source said, and Prime Minister Prayut Chan-o-cha was told about the plan yesterday morning.
The rescue mission could begin over this weekend, but no decision has been made whether to proceed, the US official said.
According to a source at the Royal Thai Navy, Thai Seals and foreign divers were mapping out preparations to rescue the 12 young footballers and their coach.
A nine-member engineering team sent by billionaire Elon Musk is preparing to help with rescue efforts, officials said yesterday.
One of the engineers was already in the country on holiday and two more were to arrive yesterday evening, followed by the remaining six today, said Lt Gen Werachon Sukondhapatipak, a deputy government spokesman.
Lt Gen Werachon said the team sent by Mr Musk, best known for electric cars, batteries and tunnelling technology, might provide help such as trying to drill a tunnel to save the group.
However, the inventor and entrepreneur have also floated some other ideas.
Mr Musk, who studied physics, has suggested using a double-layer Kevlar pressure pod or a long inflatable air sock to penetrate the narrow passageways and provide a rescue conduit.
The tubes and pods are being built in the US, a spokesman said. Some equipment is travelling with the team and some will be express-shipped.
"No need for SCUBA mouthpiece or regulator," he wrote on Twitter about his suggested pods.
"Training unnecessary & less susceptible to panic attack."
Mr Musk said the devices were being tested on Friday afternoon in a pool with a subject who had never been scuba diving.
Any air sock or tube would have to be tough enough to withstand high water pressure -- potentially two tonnes of force at a depth of 4-5 metres -- and sharp rocks, Douglas Hart, a professor of mechanical engineering at the Massachusetts Institute of Technology, told Bloomberg News.