MAE SAI, Thailand (AP) — Expert divers Sunday rescued four of 12 boys from a flooded cave in northern Thailand where they were trapped with their soccer coach for more than two weeks, as a dangerous and complicated plan unfolded amid heavy rain and the threat of rising water underground.

Eight of boys and the coach remained inside the Tham Luang Nang Non cave complex as authorities paused the international effort until Monday to replenish air tanks along the treacherous exit route.

But the success of the initial evacuation raised hopes that all will be out soon, although officials said could it take up to four days to complete.

“The operation went much better than expected,” said Chiang Rai acting Gov. Narongsak Osatanakorn, who is overseeing the mission.

He told reporters that four boys were brought out and taken to the hospital in the town of Chiang Rai, the provincial capital, for evaluation, and the next phase of the operation will resume after about 10-20 hours.

The names of the rescued boys were not released.

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.

Narongsak had dubbed Sunday to be “D-day” as the complicated effort was launched in the morning.

He said 13 foreign divers and five Thai navy SEALs were taking part in the key leg of the rescue: taking the boys from where they have been sheltering and through dark, tight and twisting passageways filled with muddy water and strong currents.

Two divers were to accompany each of the boys, all of whom have been learning to dive only since July 2, when the first searchers found them.

Cave rescue experts consider an underwater escape to be a last resort, especially with people untrained in diving.