Cave divers in Thailand have resumed the high-risk operation on Monday (July 9) to extract the remaining eight boys and their football coach from a vast flooded cave system, the head of the mission has said.

Four boys were brought safely out of the cave on Sunday (July 8), reports the BBC.

But the mission was paused overnight for air tanks to be replaced.

The boys became trapped in the cave on 23 June after heavy rains caused flooding, but were 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.

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.

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.

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.

BDST: 1615 HRS, JULY 9, 2018
AP