Thai authorities confirmed the second phase of the operation to rescue a youth soccer team trapped in a flooded cave was underway.
Chiang Rai acting Gov. Narongsak Osatanakorn said the second phase began at 11am (4pm, NZ time) and authorities "hope to hear good news in the next few hours."
Nine people remain trapped in the cave.
Authorities have been rushing to extract the boys, ages 11-16, and their coach from the cave as monsoon rains bore down on the mountainous region in far northern Chiang Rai province. Authorities said heavy downpours overnight did not raise water levels in the cave, where workers continue to pump water out.
"The factors are as good as yesterday ... The rescue team is the same team with a few replacements," Narongsak Osatanakorn, the head of the joint command centre coordinating the operation said.
He added: "The water level is not worrisome ... Yesterday's rain did not affect water levels inside the cave."
The four boys pulled from the cave Sunday in an urgent and dangerous operation that involved them diving through the cave's tight and twisting passages were in good health.
Still, they were undergoing medical checks in a hospital and were not yet allowed close contact with relatives due to fear of infections, who were able to see them through a glass partition.
Most of the same divers who took part in Sunday's rescue would return to extricate the others as they know the cave conditions and what to do.
He had said fresh air tanks needed to be laid along the underwater route.Prime Minister Prayuth Chan-ocha was scheduled to visit the site later Monday.
A Thai navy official told CNN: "The operation has begun and it is ongoing at the moment."
Earlier, rescuers woke to gloomy skies and potential thunderstorms following a night of heavy monsoonal rains lashing the mountainous region. The rain raises concerns that rising floodwaters in the cave complex will complicate rescue efforts and affect the evacuation.
Officials have said storms forecast for Chiang Rai province in Thailand's far north had factored into their decision to go ahead with a complicated and dangerous plan for the boys aged between 11 and 16 and their coach to dive out of the cave.
Thailand's Meteorological Department said there was a 60 per cent chance of rain with more thunderstorms forecast throughout the week.
Four of the boys were rescued yesterday, but nine remain underground including their 25-year-old fooitball coach, Ekkapol Chantawong. The second leg of the operation was placed on hold overnight as oxygen tanks were replenished and defibrillators put in place should the rescue take a bad turn. There are reports the divers re-entered the cave around 1pm local time Monday.
Thailand's Interior Minister Anupong Paojinda revealed the same divers who rescued the four boys will also conduct the next operation because of their knowledge of the terrain.
/arc-anglerfish-syd-prod-nzme.s3.amazonaws.com/public/3SEJ4DWUSFCPVJD3E4SDH7PN5M.jpg)
In a statement released by the government, Mr Paojinda said officials were meeting Monday morning local time about how to extract the remaining nine people from the cave in the country's north. Mr Paojinda said more air canisters were being placed along the underwater route to where the boys and their coach have been trapped for almost two weeks. He said that process can take several hours
The extraction of those remaining is expected to take another two to four days, depending on conditions. Foreign Minister Julie Bishop this morning said lessons from the initial effort would be applied as two more groups of four are brought out of the cave.
"The fact that it took so many hours underscores how precarious this whole mission is," she said. It's unlikely the nine in the cave are aware their teammates were rescued successfully, due to a lack of communication tools between them and the entrance, according to Ten News reporter Daniel Sutton. Experts say it's crucial for their survival that the remaining boys are told of the positive news
Thai governor Narongsak Osottanakorn described the first rescue as "our masterpiece work" and claimed the four rescued boys were in "perfect" health — despite earlier reports that one was being "closely monitored". Contrary to initial reports it's now believed the weakest boys were selected to come out first, following an assessment by Adelaide cave diver and anaesthetist Dr Richard Harris.
Upon exiting the cave, they were evacuated by helicopter and ambulance to hospital in Chiang Rai province, where they remain.
According to CNN, the boys will spend a day or two in isolation, inside a sterilised isolation unit, as a health precaution.
The Guardian reported that the four boys who were rescued last night are in good overall health and should be able to see their families later today, according to a key health official.
"Visitors will only be allowed to meet and talk to the patients," he said. "No hugging or touching and they [visitors] need to leave a one to two metre distance from the patients until the results of their blood tests come back."
Thongchai said doctors were checking to make sure the children are free from serious infections such as leptospirosis and meliodosis.
/arc-anglerfish-syd-prod-nzme.s3.amazonaws.com/public/3GUEKK26KZFRXFFUA7HDNVYZF4.jpg)
Authorities have so far refused to release the identities or conditions of the four who have escaped.
"Don't ask these kinds of questions. Not wise questions to ask," Prime Minister Prayut Chan-O-Cha told reporters in Bangkok on Monday morning when asked about the conditions of the four.
