CHIANG RAI, THAILAND: Twelve boys and their soccer coach found alive after ten days trapped deep inside a flooded cave will have to bear their ordeal for longer while rescuers work out how to bring them safely out, the governor of Chiang Rai province said on Tuesday.

Divers struggled through narrow passages and murky waters to discover the boys late on Monday night on an elevated rock about 4 kilometres (2.5 miles) from the mouth of the cave.

A video shot by rescuers in flickering torchlight revealed boys clad in shorts and red and blue shirts sitting or standing on the rock above an expanse of water.

"How many of you are there - 13? Brilliant," a member of the multinational rescue team, speaking in English, tells the boys. "You have been here 10 days. You are very strong."

"Thank you," one of the boys says.

One of the boys asks when they will get out of the cave, to which the rescuer answers: "Not today. You have to dive."

Two British divers, John Volanthen and Rick Stanton, were first to reach the boys, having had strong experience in cave rescues, according to Bill Whitehouse, the vice chairman of the British Cave Rescue Council (BCRC).

They found the group along with a team of Thai navy SEAL divers.

Rescuers had been focusing on an elevated mound, which cavers have named "Pattaya Beach", in the cave complex's third chamber, knowing that it could have provided the boys with a refuge when rains flooded the cave.

"The SEALs reported that ... they reached Pattaya Beach which was flooded. So they went 400 metres further where we found the 13 ... who were safe," Narongsak told the cheering group of reporters.

JUBILATION The boys survival was greeted with jubilation nationwide by Thais who have followed every twist of the harrowing story. Relatives of the boys, who have been at a shelter near the cave hoping for a breakthrough, were seen cheering, smiling and receiving calls after being given the news. Rescuers shook hands and congratulated each other as occasional cheers broke out.

Aged between 11 and 16, the boys went missing with the 25-year-old after soccer practice on June 23 after they set out to explore the Tham Luang cave complex in a forest park near Thailand's northern border with Myanmar. Rescuers now have to decide how best to get the group out in their weakened condition. They have been given energy gels to sustain them while a plan is worked out to bring them to safety.

Options considered included waiting until water levels subsided, or teaching the group to use diving gear to navigate the flooded cave.

"If you ask me now while we are still assessing all sides then I don't think they will be home soon," Chiang Rai governor Narongsak Osottanakorn told reporters.

The group's health was assessed overnight by medical teams which will continue to check the health of the group on Monday, said Narongsak, explaining that the boys had sustained light injuries.

"We categorized their health condition as red, yellow or green, red being the most severe injuries, yellow being mild and green being light. Yesterday, unofficially, we assessed that most are in the green category," said Narongsak.

Narongsak said rescue workers would now focus on the "rescue" phase and then a handover to medical teams waiting outside the cave.