Eight of boys and the coach remained inside the Tham Luang Nang Non cave complex as authorities paused the global effort until Monday to replenish air tanks along the treacherous exit route.
"Now and in the next three or four days, the conditions are ideal [for evacuation] in terms of the water, the weather and the boys' health", Narongsak told reporters.
Narongsak Osottanakorn, who has been leading the operation, then confirmed that 18 divers had gone in to get the boys.
A mammoth response operation including a medical unit, ambulance and helicopter for every boy is waiting outside the cave for the team to emerge.
"Today is D-Day", Mr. Narongsak had earlier told reporters.
Expert divers worked together to rescue guide the boys out through the narrow passageways of the cave.
Officials said the rescue could take three to four days to complete depending on the rainfall. The boys had moved 400 meters further in as the ledge had become covered by water.
Rescuers have conceded that evacuating the boys is a race against time with monsoon rains expected to undo days of around-the-clock drainage of the deluged cave. That along with dwindling oxygen levels, added to the urgency of getting the team out.
The expedition started normally but things took a wrong turn when the group reportedly got stranded in the dark tunnels by a sudden inflow of water into the caves from the heavy rain.
The order to leave the site came as irritation over the media presence grew, and a day after the rescue mission chief said conditions were flawless for the evacuation to begin. Officials went on to say the next cave rescue attempt will take place in 10-20 hours.
The letters were picked up by Thai navy SEALs who made an 11-hour journey back-and-forth to act as postal couriers. The rising water filled large stretches of the cave, cutting off the team's escape route and keeping rescuers from finding the team for 10 days, CBS News noted.
The ordeal has riveted Thailand and captured the world's attention.
The Thai government released a graphic showing how the rescue from the Tham Luang cave would occur.
U.S. President Donald Trump said the United States was working "very closely" with the Thai government to free the boys."Very fearless and talented people!" he tweeted. Very courageous and talented people!
- Family comes before president, says Trump lawyer
- Longtime Spur Parker to sign with Hornets
- Rodriguez misses out for Colombia, Alli back for England
- Severe Rain, Flooding Leave 38 Dead, Scores Missing in Japan
- White House Taps Former Fox News Executive For Senior Communications Job
- Donald Trump urged to avoid controversial Supreme Court pick
- SCOTUS: Trump interviews senator as possible replacement for Kennedy
- Boys lost in Thai cave to be taught how to dive
- Elon Musk offers engineers to help with Thailand cave rescue
- Lucas Torreira: Arsenal set to complete signing of Uruguay midfielder