Mae Sai (Thailand): Expert divers have 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 operation unfolded amid heavy rain and the threat of rising water underground.

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

Extracting everyone could take up to four days, but the initial success raised hopes that could be done.

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

He told reporters the four rescued boys were 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.

Narongsak 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 the 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.

The death Friday of a former Thai navy SEAL, Saman Gunan, underscored the risks. The diver, the first fatality of the rescue effort, was working in a volunteer capacity and died on a mission to place oxygen canisters along the route.

But Narongsak said earlier that recent mild weather and falling water levels had created optimal conditions for an underwater evacuation. Those conditions won’t last if the rain resumes, he said.

The potential for rising water and the dwindling oxygen levels added to the urgency of getting the team out. Efforts to pump water out of the cave have been set back by heavy downpours.

Monsoon flooding cut off their escape route and prevented rescuers from finding them for almost 10 days.

The ordeal has riveted Thailand and captured the world’s attention. The search and rescue operation has involved dozens of international experts and rescuers, including a US military team.

Elon Musk’s Space X rocket company tested a “tiny kid-sized submarine” that could potentially help the children through the narrow, flooded cave passageways. A spokesman for Musk’s Boring Co. tunnelling unit, which has four engineers at the cave, said in an email yesterday that Thai officials had requested the device.

If the tests were successful, the sub would be placed on a 17-hour flight to Thailand. He posted a video of a diver testing the device in a pool.