Rescuers in Thailand were no closer today to deciding when and how to extract 12 boys and their soccer coach from a flooded cave complex, where they were found this week, pale and weak but otherwise in good health, after nine days lost underground.

The dramatic search and rescue operation for the junior soccer team, who disappeared in the cave in the northern province of Chiang Rai on June 23, had seemed to be nearing an end when a team of British and Thai divers found the boys late on Monday, clustered on small, muddy bank in a flooded chamber.

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But attention has now turned to how to get the group back out through several kilometres of dangerously flooded tunnels.

The navy has raised the possibility that the 13 could be in the Tham Luang cave in Chiang Rai province until the flood waters recede, at the end of the rainy season in four months.

But others say the boys could be out in a matter of days if the weather is on their side and water can be pumped out of the cave complex, and if they can be taught to use scuba gear.

Kobchai Boonarana, deputy director-general of the Disaster Prevention and Mitigation department, said it was up to the rescue team in the cave to decide whether and when the boys would be strong enough to tackle the journey out.

"Their conditions, we can see that their morale is good but what about their strength and their ability? That's up to the team inside to decide," Kobchai told reporters on Thursday.

"Our job is to keep pumping out water and it is up to the team inside to assess the safety level and whether the kids can travel safely through," he said.

Some relatives of the boys gathered near the cave early on Thursday, where a few rescuers were marching up to its entrance, a contrast to days of frantic activity during a search that has grabbed media attention around the world.

One mother said she had still not been able to contact her boy.

"We can't send them messages yet," said Ratdao Chantrapul, 37, the mother of 14-year-old Prajak Sutham.

"Yesterday, they tried to take in mobile phones but the bag it was in broke," she said.

Rescuers had to contend with days of heavy rain that flooded the cave complex at the beginning of the search but the weather has been relatively dry for the past four days.

Rescuers have sent in food, water and medical staff while they have been pumping water out of the tunnels in a bid to lower water levels to help with the rescue.

But the meteorological department warned on Thursday that up to 60 percent of the country's north, including Chiang Rai, can expect heavy rain from July 7 to July 12.