Twelve boys and their football coach remain missing, believed lost, in a deep cave in northern Thailand. A huge search and rescue operation launched by the Thai authorities has been hampered by heavy rain, which is causing water levels in the cave to rise quickly. Nonetheless, the families of those missing say they are hopeful all will be found alive. Tony Cheng sent this report from Tham Luang cave in Chiang Rai.

The long and tortuous wait for the parents and relatives of the 12 boys trapped inside the caves. For some, it was simply too much, while others waited stoically in the rain. This woman is the Aunt of Aek, the 25 year old coach who took the boys into the cave. She said he'd only been inside once in the last few years, but she was sure he would do anything to protect his charges.

KHAM CHANTAWONG AUNT OF FOOTBALL COACH "He took very good care of the kids. They all got on very well together. The children never fought or even cursed at each other."

The rescue site is now swarming with people. The plight of the thirteen has attracted huge attention in Thailand, and around the world. But the conditions aren't helping their cause.

TONY CHENG CHIANG RAI "This is the main command and control center coordinating the rescue effort. And there are an enormous number of people drafted in, both the army, military and civilian search and rescue teams, but the rain is coming down heavily, the whole area is swathed in mud, that's making everything inconvenient out here, but inside the caves, where the water level is rising fast, it's getting very dangerous.”

On Tuesday more search and rescue teams went into the caves, fully equipped to dive in what is now deep water. But apart from an abandoned phone and a pair of shoes, no signs of life. British cave expert Vern Unsworth knows this cave intimately and has been advising the rescue teams. He's already been inside twice.

VERN UNSWORTH MAE SAI RESIDENT & CAVE EXPERT "If they're in the right place they can survive for 5-6 days. But the water now, the floodwater, is getting higher and higher, so there will be a point in time where even this cave here, the entrance will close."

Further down the mountain, a desperate attempt to pump water out of a lake, to allow the caves to drain. But in the heavy rain, it was having little impact. And as day four draws to a close, the army sent in an extra thousand troops to add their support. But manpower alone will not do much, and at this stage, the missing boys need help from a higher authority. Tony Cheng, CGTN, Tham Luang Cave, Chiang Rai, Northern Thailand.