A massive global effort involving more than 100 divers and rescue workers brought the first eight boys out through winding and partly-submerged passageways on Sunday and Monday, four a day.
Rescuers resumed preparations on Tuesday for a third rescue operation deep into a cave complex in northern Thailand to free four remaining boys and their soccer coach in a race against time and monsoon weather.
Two of the boys had suspected lung infections but the four boys from the first group rescued were all walking around their hospital beds.
Reuters reported that eight players have been rescued in risky attempts by a world-class global team of divers.
"Mini-sub is ready if needed", Musk tweeted, adding, "Leaving here in case it may be useful in the future".
The rescue mission began on Sunday morning, almost a week since the 12 boys, aged 11 to 16, and their coach had been discovered on an embankment 2.5 miles (4 kilometers) inside the winding tunnels.
Rescuers in Thailand ended day two of their mission with four more boys freed from the Tham Luang caves on Monday.
In total, 13 foreign cave divers and five Thai navy SEALs participated in Sunday's rescue, according to Reuters.
The group had gone for a trek when heavy rains trapped them in a dark, cramped chamber 2.5 miles inside in the Tham Luang Cave system.
However, the boys and their coach are facing malnutrition, dehydration and other unknown ailments.
He added, "They still need to be kept away from their parents and others due to fear about infection".
The same divers who rescued the children on Sunday went back in to collect the next four on Monday, with the country's interior minister Anupong Paojinda saying they would conduct the next operation as they already knew of the cave's conditions and how to safely bring the children out.
Speaking at a press briefing at 9.30 pm, the former Chiang Rai governor said that the extraction mission today which began at 11 am was accomplished at 8 pm with four more teenage footballers being rescued out of the flooded cave and safely sent to Chiang Rai Prachanukroh hospital.
"If the rain god helps us, then we may be able to work fast", the head of the rescue mission, Narongsak told reporters.
As we enter the day three of the Thai cave rescue mission, the public health permanent secretary Dr Jesada Chokedamrongsuk, from the Ministry of Public Health and Chiangrai Prachanukroh Hospital, spoke to the media this morning (local time) about the health of the eight boys who have been rescued so far.
The "Wild Boars" team became trapped on June 23 when they set out to explore the cave after soccer practice and rains flooded the tunnels.
For the first four rescues on Sunday, two divers accompanied each boy, one from the side and one from behind. The eight boys were rescued from the flooded cave.
Chiang Rai acting Gov. Narongsak Osattanakorn said the second phase began at 11 a.m. and authorities "hope to hear good news in the next few hours".