Rain was now the biggest worry, said Narongsak Osatanakorn, the governor of Chiang Rai province, who is coordinating the rescue efforts. “I’ve asked the meteorological department to check the weather forecast and report to us daily,” he said.

A fibre-optic cable was being laid inside the cave and would reach the boys soon, he added, so the children would be able to speak to and possibly see their parents on video.

With wet weather looming, authorities are also calculating how long they are willing to allow rescuers to remain in the cave before they order an evacuation – one that could cut the boys off for up to four months.

Updates on the condition of the boys and the water levels were being slowed by the length of the journey to reach the children. “It’s about 11 hours – six on the way from the entrance to where the kids are and five on the way back,” he said.