A witness near the cave told the Reuters news agency that medical workers carried four people to emergency rescue vehicles. Four of the trapped Thai cave boys were rescued over the weekend, and on Monday, four more were transported to the hospital.
The worldwide effort to save the group has paired divers in "buddy teams" with the remaining eight boys and their coach.
Narongsak would not identify the rescued boys. They were missing for nine days before being discovered by British divers last week.
Thai officials had said Sunday that they were temporarily suspending the rescue effort so they could replenish oxygen supplies and other gear.
"If we wait and the rain comes in the next few days we will be exhausted again from pumping and our readiness would drop".
The rescue team went into the cave to resume the operation at 11 a.m. (0400 GMT), the chief of the rescue mission, Narongsak Osottanakorn, told a news conference earlier, adding he expected good news.
Thai Royal Navy inside the Tham Luang cave on July 7.
Authorities in northern Chiang Rai province began the unsafe mission to bring out the 12 boys and their coach earlier on Sunday.
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 16-day-long ordeal of four boys, who were part of a 13-member group, trapped in a flooded cave system in Thailand ended Sunday as they were brought out safely by rescuers.
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Eight members of the soccer team stranded in a flooded cave complex in Thailand have been saved, as rescue efforts continued for a second day.
Multiple calls to senior government officials and military personnel leading the rescue operation rang unanswered Monday evening. There was no word on the condition of any of the people brought out on Monday.
Authorities had been rushing to extract the boys and their coach from the cave as monsoon rains bore down overnight on Sunday.
The four boys pulled from the cave Sunday in an urgent and unsafe operation that involved them diving through the cave's tight and twisting passages were in good health. Their families were being kept at a distance because of fears of infection and the emaciated-looking boys were eating a rice-based porridge because they were still too weak to take regular food, authorities said. Through a translator, he says people keep thinking about the teammates trapped underground and that "everyone is trying to help the families".
1 NEWS' Kimberlee Downs has the latest from Chiang Rai.
He also tweeted that SpaceX and Boring Co. engineers were headed to Thailand to see whether they could assist Thai authorities.
"Cave disease" is also a concern, multiple media reported.
Thai officials started the rescue operation on Sunday as weather experts predicted more rain in the coming weeks.
"We have not been told which child has been brought out ..."
Relatives said the boys had been inside the labyrinthine complex during the dry season.
Thai public television has aired live video of a medivac helicopter landing close to a hospital in the city of Chiang Rai, near the site of the cave where a youth soccer team has been trapped for more than two weeks.