Although rescue workers in Thailand on Monday brought four boys safely out of a labyrinthine flooded cave complex where a 12-member soccer squad and their coach were trapped for more than two weeks, taking the total number rescued to eight.

The rescue workers are making final preparation to bring back remaining five today.

The mission to save all the trapped is a race against the clock with heavy rain expected this week which would again flood the tunnels with fast-flowing, rising water.

“All four boys have arrived at hospital, all are safe,” Narongsak Osottanakorn, head of the rescue mission, told reporters of those rescued on Monday.

Asked whether the remaining four “Wild Boars” team members and their coach would come out at the same time in the next rescue effort, he said: “It depends on the plan… We have set the plan for four people so if they want to take five out (at the same time), then they need to change the plan.”

The dramatic and dangerous rescue at the Tham Luang cave in the northern province of Chiang Rai was launched on Sunday and four boys were brought out that day. All the boys were in good condition, Narongsak said.

The operation on Monday went more smoothly than on Sunday and took two hours less as the practice became more refined, he said.

Prime Minister Prayuth Chan-ocha visited the cave to inspect the rescue operation, with navy rescuers giving him a rousing cheer.

“The prime minister said that this kind of event should never happen again on Thai soil,” Narongsak told reporters. “We should learn from this experience to prevent it from happening again.”

The Thai navy SEAL unit, which has been overseeing the rescue, confirmed on its Facebook page that the total number of boys brought out was eight.

“The rescue has been immense,” said volunteer helper Somjit Saenset, 56. “I’m so happy the children came out safely. I want to send my moral support for all involved” in the rest of the mission.

The Wild Boars and their coach became trapped on June 23 when they set out to explore the vast cave complex after soccer practice, when a rainy season downpour flooded the tunnels.