All 12 boys and their football coach who were missing for nine days after becoming trapped in a cave in Thailand have been found alive, officials have said.

In video shot by rescuers as the group was found, torchlight reveals boys in shorts and red and blue shirts in an underground cavern beside an expanse of water.

Two British volunteer cave divers found the boys in a dry air space south of the Pattaya Beach area of Tham Luang Nang Non Cave, which is thought to be between 800m to 1km below the surface, the British Cave Rescue Council said.

“How many of you are there – 13? Brilliant,” one rescuer tells the boys. “You have been here 10 days. You are very strong.”

One boy replies: “Thank you so much.”

The children, aged between 11 to 16, and their 25-year-old coach were exploring the Tham Luang caves on 23 June when they became trapped.

A happy family member shows the latest pictures of the missing boys taken by rescue divers inside Tham Luang cave after all members of the group were found alive ( AFP PHOTO / LILLIAN SUWANRUMPHALILLIAN SUWANRUMPHA/AFP/Getty Images) (AFP)

A massive international rescue effort has been underway since, trying to reach the group in the cave network that stretches 10km (6 miles) into a mountain.

The work has been hampered by rising waters and mud, but divers changed their tactics on Sunday, deploying a rope line and extra oxygen supplies.

Chiang Rai Governor Narongsak Osatanakorn said on Monday the 13 were in the process of being rescued.

“We found them safe. But the operation isn’t over,” he said.

Rescuers had discussed waiting until water levels subside, or pumping water out of the cave, to get the boys out. But more heavy rains are expected.

Other options include teaching the group to use diving gear to navigate the flooded cave, but experts branded the option ”risky”.

Medical teams were seen preparing first aid kits after news of the group’s discovery broke outside the cave’s entrance.

Mr Narongsak said medical teams had been sent inside the cave and it would take them around four hours to assess the group’s health and how fit they are before coming up with a strategy to get them out.

Family members of one of the missing boys celebrate while camping out near Than Luang cave following news all members of children’s football team and their coach were alive in the cave at Khun Nam Nang Non Forest Park in the Mae Sai district of Chiang Rai province (AFP PHOTO / LILLIAN SUWANRUMPHALILLIAN ) (AFP PHOTO / LILLIAN SUWANRUMPHALILLIAN)

The boys have been provided with energy gel to eat, the Thai navy SEAL unit said on its official Facebook page.

After news of the group’s discovery, Thailand’s prime minister thanked international experts who helped with the rescue effort.

A statement released by the prime minister’s office said Prime Minister Prayuth Chan-ocha “wishes to thank the tremendous efforts of all international units that have come to assist the Thai authorities in rescuing the youth football team that was stuck in the caves in Chiang Rai”.

It added: “The Royal Thai Government and the Thai people are grateful for this support and cooperation, and we all wish the team a safe and speedy recovery.”

Relatives of the boys, who have been monitoring the operation from a shelter near the cave, were seen cheering and smiling. Meanwhile, rescuers shook hands and congratulated each other.

It remains unclear whether any of the group are injured or in need of medical attention, but they have been given energy gels to sustain them while a plan is worked out to bring them to safety.

As the days wore on with the group missing, distraught family members had placed fruit, desserts, sugary drinks and sweets on mats near the cave as an offering to the spirits which some people believe protect the cave and the forest.

Thai navy divers and rescue workers from other countries made initial progress through the narrow passageway of the Tham Luang Nang Non cave early on Monday after passing through a key chamber on Sunday whose high, murky waters had previously blocked their progress.

The rescuers had been focusing on a mound inside the cave, dubbed ”Pattaya Beach”, which could have provided the boys with a refuge from the rising waters.

“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,” Mr Narongsak told reporters.

Captain Jessica Tait from the US Air Force’s rescue support team said there were “lots of challenges” throughout the search.

“There were lots of challenges when it comes to the elements, when it comes to different courses of actions,” she told reporters.

“But you know what I saw, I saw Thailand coming together.”

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The next challenge will be getting the group out of the cave, which some have dubbed a “labyrinth”.

Rescuers had discussed waiting until water levels subsided to get the boys out. Other options included teaching the group to use diving gear to navigate the flooded cave.

Medical teams were seen preparing first aid kits after news of the group’s discovery broke outside the cave’s entrance.

Mr Narongsak said medical teams had been sent inside the cave and it would take them around four hours to assess the group’s health and how fit they are before coming up with a strategy to get them out.