Cave divers in Thailand have resumed the high-risk operation to extract the remaining eight boys and their football coach from a vast flooded cave system.

Ambulances have been seen leaving the cave entrance, amid unconfirmed reports that more boys have been rescued.

Four boys were brought out safely on Sunday, but the mission was paused overnight for air tanks to be replaced.

The boys were trapped in the cave on 23 June after heavy rains caused flooding, but found alive last week by divers.

Rescuers decided to go ahead with the operation to free them because of fears that waters would rise again.

The rescue is complicated by sections in the cave involving diving - sometimes in a very confined space - and climbing.

Rescue mission chief Narongsak Osottanakorn said it had resumed at 11:00 local time (04:00 GMT).

It was expected to end by 21:00, he said. "More personnel" were being used than on Sunday.

Reporters at the site said they had seen someone taken away on a stretcher to an ambulance, and a helicopter was then seen leaving the area.

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The names of the rescued boys have not been released out of respect for the families whose sons were still inside, and they have not been reunited with their own families, the mission chief added.

He said physical contact with loved ones would be avoided until a risk of infection had passed, though contact through glass or at a distance might be allowed.

Mr Narongsak allayed concerns that recent heavy rain might have raised water levels, saying conditions were "as good as yesterday". "We should hear good news again," he added.

Rescuers took advantage of a break in the rain on Sunday to launch the mission earlier than some expected.

The first stage of the mission ran "smoothly" and the rescued boys were in "good health", according to the Thai authorities.

How are the boys being moved?

A team of 90 expert divers - 40 from Thailand and 50 from overseas - has been working in the cave system.

They have been guiding the boys through darkness and submerged passageways towards the mouth of the Tham Luang cave system.

Getting to and from where the boys are has been an exhausting round trip, even for the experienced divers.

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The process includes a mixture of walking, wading, climbing and diving along guide ropes already in place.

Wearing full-face masks, which are easier for novice divers than traditional respirators, each boy is being accompanied by two divers, who also carry his air supply.

The toughest part is about halfway out at a section named "T-Junction", which is so tight the divers have to take off their air tanks to get through.

Beyond that a cavern - called Chamber 3 - has been turned into a forward base for the divers.

There the boys can rest before making the last, easier walk out to the entrance. They are then taken to hospital in Chiang Rai.

In an indication of how dangerous the journey can be, a former Thai navy diver died in the caves on Friday. Saman Gunan was returning from a mission to provide the group with air tanks when he ran out of oxygen.

He lost consciousness and could not be revived. His colleagues said they would "not let the sacrifice of our friend go to waste".

Who are the boys and their coach?

Some details have emerged of members of the team and their coach.

Captain Duganpet Promtep, 13, is described as a motivator and highly respected by his teammates. He had apparently been scouted by several Thai professional clubs.

Myanmar-born Adul Sam-on, 14, speaks several languages, and was the only team member to be able to communicate with British divers when they were first discovered.

It was 17-year-old Peerapat Sompiangjai's birthday when the group became trapped in the cave. The snacks the boys brought with them to celebrate are likely to have helped them survive their ordeal.

Assistant coach Ekapol Chantawong, 25, was said to be the weakest of the group when they were found, as he reportedly refused to eat any of the food and gave it instead to the boys.

Read more about the team

How did the group get there?

The boys were found inside the cave by British rescue divers a week ago, about 4km (2.5 miles) from the cave mouth.

Aged between 11 and 17, they belong to a football club called the Wild Boars, and became trapped during an excursion with their coach.

It took nine days to find them in the underground network's dark depths.

Race against the rain

Officials had originally thought the group might have to stay where they were until the rainy season ended - and that could have meant months underground.

But with the rainy season just beginning, it has become clear that the flooding which originally trapped the boys will only get worse in the coming days.

Rescuers have been desperately pumping water out of the cave, and Mr Narongsak said on Sunday that water levels inside were at their lowest levels so far.

BBC.COM