Divers had earlier launched a daring and risky mission to rescue the children and their soccer coach, who had been trapped underground for more than two weeks.
The team of 18 Thai and global divers supported by at least 80 other rescue workers successfully rescued three more boys on Monday, two hours faster than the operation on Sunday. The interior minister Anupong Paojinda was noted saying that officials are meeting on Monday morning to plan the next stage of the operation in order to rescue the remaining 9 students from the cave.
The boys were immediately taken to the hospital for evaluation after being trapped underground for almost two weeks.
Asked how the authorities had decided which boys were to be taken out first, Mr Narongsak said: "Their health". They eventually found a dry landing spot, where they waited for nine days before being found by two British divers.
At a news conference Monday, former Chiang Rai governor Narongsak Osotthanakorn said the second rescue involved numerous same divers who brought the four boys out on Sunday.
His announcement, at a news conference more than an hour after helicopters and ambulances were seen rushing from the cave area, drew cheers and applause.
Sunday's mission involved 13 foreign divers and five Thai navy SEALs. General Kongcheep Tantrawanit said, referring to the area where rescue workers had set up a base.
The 12 boys, aged between 11 and 16, and their coach, 25, went missing in Tham Luang Nang Non cave in northern Thailand's Chiang Rai Province on June 23.
Expert climbers, divers and Thai Navy Seals have mulled contingencies ranging from drilling an escape route through the mountain to waiting out the monsoon inside the cave. The rescue operation has come to a close for the night and will resume in 10-20 hours.
Initial euphoria over finding the boys alive quickly turned into deep anxiety as rescuers struggled to find a way to get them out.
Guerrero says she's glad rescue operations to save the group of boys and their coach trapped in a Thai cave are moving swiftly before water levels in the cave rose even higher.
Narongsak said rescuers had to tighten a guide rope as part of their preparations for Monday's operation. "The boys are ready to face any challenges", rescue chief Narongsak Osottanakorn told reporters near the cave site.
Two ambulances have left from a cave in northern Thailand, hours after an operation began to rescue 12 youth football players and their coach.
None of the boys have scuba diving experience and experts have warned they could easily panic while swimming underwater in darkness.
But the governor supervising the mission said earlier that mild weather and falling water levels over the last few days had created optimal conditions for an underwater evacuation that won't last if it rains again. It was raining Sunday, but Narongsak was optimistic that the rescue could continue Monday. The same process was used Sunday for at least one of the four boys rescued in the first attempt at getting the 12 boys and their coach out of the underground cave complex.