He said the four boys rescued on Sunday were "hungry but in good health".
They have no fever or serious ailments, said public health permanent secretary Dr Jesada Chokedamrongsuk at a press conference on Tuesday (July 10).
The rescue operation began Sunday and has been progressing rapidly. We've started giving them "medical food" this morning. Earlier in the day, rain poured in Thailand's Mae Sai, which fueled fears of rescue mission getting complicated in the Tham Luang Nang Non cave.
The four boys rescued on Sunday were each accompanied by two divers as they were gradually extracted from the cave.
The Facebook page of the Thai Navy SEALs, who have been central to the rescue operation, was updated Monday night to say "two days, eight boars" - a reference to the Wild Boars, the name of the boys' soccer team.
Alluding to that worry, the regional army commander offered his thanks Monday to the rain god Phra Pirun, imploring him to "keep showing us mercy".
The Thai government has confirmed that rescuers have managed to free four boys from the cave in Northern Thailand where they have been trapped for two weeks.
The hazardous bid to rescue the boys - aged between 11 and 16 - started unexpectedly on Sunday when the rescue team said conditions were flawless for the evacuation.More news: Treacherous Thai cave rescue bid enters day two
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At least nine ambulances have been waiting at the site after the leader of the rescue operation said Tuesday's aim was to bring out all five as well as a medic and three Thai Navy SEALS, who have been with the trapped boys.
Headcam footage shows the treacherous path the rescuers must navigate in order to retrieve the stranded school boys and their coach.
The boys, ranging in age from 11 to 16 and their soccer coach set out to explore the cave on June 23, but became trapped after heavy rains flooded passages. The teams have risked their lives to deliver supplies and food to the children and their coach, and divers have been teaching the boys ― some of whom don't even know how to swim ― diving and breathing techniques to prepare them for their harrowing journey home.
Narongsak would not identify the rescued boys. "From what I've seen in the clip, they did look skinny", he said.
The search and rescue operation has riveted people in Thailand and internationally, with journalists from across the globe traveling to this town along the border with Myanmar to report on the ordeal.
Osatanakorn said officials did not want to waste time because of intensifying rain that could halt rescue efforts.
Interior Minister Anupong Paochinda also said the boys were in good health. The mission today is more hard than in the past two days, with all nine to be brought out. More worrying, however, oxygen levels in the cave were falling.