All 12 members of a youth football team, along with their 25-year-old coach, have now been rescued from the Tham Luang cave in Thailand's Chiang Rai Province.
American engineer arrived in Thailand, where the operation to rescue the children from the cave.
19 divers are involved in the mission to bring the last four boys and their coach to safety, and more will enter gradually through the day.
"All five will be brought out at the same time today", said the head of the rescue mission, Narongsak Osottanakornon, on Tuesday. Last week, Musk sent engineers from two of his companies, SpaceX and Boring Co., to assist Thai officials in the rescue effort, which comprises a large team of worldwide diving, engineering and medical experts, among other professionals.
At least two companies are also looking to make a film telling the story of the rescue. Rescue operations have halted for the night and will restart on Tuesday. Medical experts say they are in high spirits and generally healthy.
Three Thai Navy Seal divers and a medic are still on their way out of the cave.
"(They) will be extracted today", rescue chief Narongsak Osottanakorn told reporters, adding the journey out should be faster than on previous days.
The father of Richard Harris, a key member of the team of global experts involved in the dramatic rescue mission, died soon after all the boys were freed.
The eight boys brought out on Sunday and Monday were in good health overall, although two had suspected lung infections.
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They are all likely to stay in hospital for seven days due to their weakened immune systems.
Family members have seen at least some of the boys from behind a glass isolation barrier, and Jesada said doctors may let the boys walk around their beds Tuesday.
Four of the boys were carried out on stretchers on Sunday and four more on Monday.
"I beg Phra Pirun because the Meteorological Department said that from Monday on there will be continuous rain", Bancha said. That left four boys and the team's coach trapped inside as the operation was called off for the day. But they also warned heavy rain could hamper their efforts. Monday's mission took about nine hours, two fewer than Sunday's.
The tech entrepreneur tweeted Tuesday morning he'd "Just returned from Cave 3", referring to the rescuers' command center inside the sprawling cave.
Musk posted videos and photos of divers testing out the submarine in a Los Angeles pool.
Narongsak would not identify the rescued boys.
Importantly, as of the time of this writing, eight of the 13 trapped people have already been saved by the heroic actions of rescue divers and support teams.