There was no word on the condition of any of the people brought out on Monday.
An official briefed on the rescue operation said Monday the rescued kids haven't yet been served the chicken dish but are starting instead with lighter blander food such as diluted porridge.
Authorities have not revealed at this stage when the rescue operation would resume for the remaining four boys and their coach, who have been trapped in the cave since June 23.
The unsafe bid to rescue the boys - aged between 11 and 16 - resumed after a break on Sunday night to replenish oxygen supplies and make other preparations deep inside the cave complex in northern Thailand'sChiang Rai province.
Narongsak Osatanakorn, the former Chiang Rai governor who's been heading the rescue operation, said the four children had to dive more than half a mile to get to safety.
On Sunday, teams of divers brought out four of the trapped boys but waited several hours before confirming their safe rescue. "We can't visit our boys in hospital because they need to be monitored for 48 hours", Somboon told Reuters.
Narongsak said last week they would bring the fittest people in the group out first. So the sub still could come into play on a third day of rescues.
The rescue team consists of 90 divers, 40 from Thailand and 50 from overseas.
Saman Gunan had been on his way back from taking air tanks to the trapped boys when his own air supply ran out.
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.
Officials will be meeting late Monday to discuss Tuesday's plan. Musk said his submarine has eight handles, four in the front and four in the rear, and four air tank connections.
Divers took about four hours to escort the four from the ledge to the chamber, the source added.
The Thai official leading the operation to save the 12 boys and their coach from the flooded cave in northern Thailand said the rescue has been going "better than expected". They were stranded by flash floods that caused water levels to rise, making it hard to get out. Four boys and their coach remained inside the cave. Thailand's Meteorological Department said there was a 60 percent chance of rain Monday with thunderstorms forecast throughout the week, the Associated Press reported.
On Sunday, Musk tweeted a series of videos showing a team of divers testing the pod in the swimming pool at Palisades Charter High School. An international-level rescue mission began soon after, with hundreds of experts and military personnel from various countries arriving at the spot. But it began raining heavily just after the first boys were rescued. Ten days later, rescuers located the team and started a hazardous mission to evacuate them.
Finally, Elon Musk tasked SpaceX engineers with crafting a special tiny submarine that could be used during the rescue, and the tech guru says the device is operational.
Narongsak said earlier on Sunday the mission may take three or four days to complete. A family member told CNN Monday that they hadn't been told which boys had been pulled out, and who is still trapped in the cave.
At the hospital in Chiang Rai, green canvas sheets had been put up to block the entrance from view.