The 13 were trapped during a visit on June 23 when monsoon floods blocked the cave exit and forced them back three miles into the mountain - where they have stayed on a ledge starving in the darkness. 'Doctors have told us we must be careful about the food that is given to them because they are fragile after starving for many days.
He added that the divers were the "same multinational team" that rescued the four boys on Sunday.
A health official earlier described the mental and physical condition of the eight rescued so far as "good", adding they will be kept in hospital for around a week.
They have no fever or serious ailments, said public health permanent secretary Dr Jesada Chokedamrongsuk at a press conference on Tuesday (July 10).
The boys had a good appetite but were mainly being given bland, easily digestible foods.
Complex and narrow, the system is not dissimilar to the caves being navigated by rescue divers in Thailand. Another two more boys left the cave complex a short time later followed by the fourth boy.
Underscoring the danger behind the mission, Ivan Karadzic said, "They are diving in something considered an extremely hazardous environment".
Phuwadech Kamnguen, a 14-year-old best friend of one of the trapped boys, said he's looking forward to eating KFC with the team again.
The boys' nightmare experience - trapped in claustrophobic darkness by rising waters - resonated across the globe, riveting people both in Thailand and internationally who anxiously watched the news coming from this town along the border with Myanmar.
Narongsak Osot-tanakorn, Former Governor of Chiang Rai who heads the rescue operation, said divers hope to rescue the last four boys and their coach from the cave Tuesday.
The 31cm-wide custom submarine would make the boys passive participants in the rescue and could potentially shorten the journey, which took divers a total of nine hours in the second successful rescue operation on Monday. "We had imagined all sorts of catastrophic situations - equipment breaking, children panicking", he said, adding that the officials had backup options in mind in case anything falls apart. Thirteen foreign divers and five members of Thailand's navy SEAL unit are taking part in the rescue operation. It ended with their fighting cheer, adopted from the U.S. Navy: "Hooyah!"
All preparations, including replacing the oxygen cylinders positioned along the route out in the cave, take at least 20 hours, he said. If the rain god helps us, then we may be able to work fast.