Almost 20 Australians work on Thai rescue

Foreign Minister Julie Bishop has welcomed the rescue of four boys from a cave in northern Thailand, as 19 Australians continue to work on the precarious rescue operation.

Ms Bishop said the Australian contingent had been integral in the first stage of the rescue mission, with the eight remaining boys and their soccer coach still in the cave waiting to be extracted.

"It's highly dangerous, it's very precarious and our thoughts are not only with the boys but also with the diving and rescue teams that are assisting," Ms Bishop told the Nine Network on Monday.

The mission's initial success has raised hopes for those still trapped, but officials say it could take four days to complete the entire rescue.

Ms Bishop said lessons from the initial effort would be applied as two more groups of four are brought out of the cave.

"It's wonderful news and we are very relieved that the four boys have been evacuated," Ms Bishop said.

"But the fact that it took so many hours underscores how precarious this whole mission is."

Australian Federal Police and Defence Force divers, along with Adelaide cave diver and anaesthetist Richard Harris are part of the team working on the rescue.

Ms Bishop said Dr Harris was involved in the medical assessment which determined the first four boys were fit enough to swim to freedom.

"His qualifications and experience were certainly in demand," she said.

Related: Thai cave rescue live update blog