Wang said it is too difficult to dig another entrance and this could take a long time.

"Besides, all the resources－rescue personnel, equipment, etc.－are concentrated on the water side."

Wang said the rescue team is teaching the boys how to dive and overcome their fear after they recover their strength. Meanwhile, the team is working on the construction of "chamber three", a cavern used as a base to store food, oxygen tanks and diving gear, and also a transfer station between its shelter and the cave entrance.

"We Chinese rescuers have undertaken a lot of tasks, such as shipping the material, constructing the underwater transport corridors and clinic system as well as taking part in making rescue plans," Wang said.

"It may take four, five or even more days until we can finally bring them out under the current weather conditions," he said.

Wang disagrees with many who predict the soccer team can be rescued within a week.

"Besides, the rain is coming, and it will slow our pace. We need to do a lot before we can bring them out. We need to prepare for several scenarios," he said. "Rescue is not a one-step process."

Wang and his team decided to join their international colleagues when they saw breaking news of the soccer team's plight, and applied to the authorities in China and Thailand. "We really want to use the experience we have accumulated since the Wenchuan earthquake in 2008 to help those who are suffering."

They arrived in Chiang Rai with their equipment on Friday and immediately set to work.