Rescuers’ hopes of guiding 12 trapped schoolboys from their underground hell are soaring after a break in the weather has seen water levels dropping in the cave system where they have been trapped since June 23.

Narongsak Osatanakorn, the regional governor leading the massive rescue effort, said the fate of the boys and their soccer coach will be determined in part by the imminent arrival of two big groups of volunteer divers.

After that, when the fresh divers are ready to enter the underground complex and depots of oxygen tanks are in place along the route, implementing the complex retrieval bid will depend entirely on the weather.

In further signs the rescue is poised to begin in earnest, all non-essential personnel were ordered to leave the scene as a fleet of ambulances arrived, ready to ferry to boys to hospital as they are brought to the surface.

“Assessing the situation now, it is necessary to evacuate the area for the rescue operation,” Mae Sai police commander Komsan Sa-ardluan said.

“Those unrelated to the rescue operation, please evacuate the area immediately.”

According to ABC correspondent Anne Barker the long-planned effort might already be underway, a possibility Thai authorities have so far declined to confirm or deny.

“The plan that I’ve held on to from the beginning is that we have to bring the kids out and the determining factor of this plan is to have as little water as possible,” Mr Osatanakorn said.

But he stressed that while floodwaters have receded as much as is thought likely, “if it rains and adds to it again, we don’t know what other risk factors we will have to face”.

Rescue leaders cautioned that, while conditions are the best they have been to date, the actual extraction might not begin for as long four days as other risks and logistics are factored in.

High carbon dioxide levels in the cave are a known hazard, he said, lamenting the death of a volunteer diver who perished for lack of oxygen deep within the labyrinth.

Yet despite the risks ahead and a drilling-rig accident that saw two workers injured, the massive rescue team’s morale has soared after the trapped boys and their coach, 25-year-old Ekapol Chanthawong, sent out a bundle of notes to anxious parents waiting at the cave entrance.

“I want to eat pan-fried pork” was just one of many heart-lifting and heart-breaking messages written by the schoolboys, all members of the Wild Boars soccer team, who have now endured 15 anguished days and nights in northern Thailand’s Tham Luang cave complex.

“Don’t worry, everyone is strong”, assured another brave note, while coach Chanthawong has apologised to their parents.

“The kids are all fine, the crew are taking good care. I promise I will care for the kids as best as possible. I want to say thanks for all the support and I want to apologise to the parents.”

Other notes from the boys, all between 11 and 16, spoke of hunger and how much they longed to taste their mothers’ cooking and favourite dishes.

“When we get out of here, we want to eat many things. We want to go home as soon as possible,” reads one message, handwritten in blue ink on notebook paper and carried out by a foreign rescue diver late on Friday.

A total of seven pages were posted on the Thai Navy SEALs Facebook page.

“I want to eat pan-fried pork,” one of the boys aged 15 writes, with others yearning for fried chicken and “grandma’s pork crackling with dipping sauce”.

“I’m doing fine but the air is a little cold but don’t worry. Although, don’t forget to set up my birthday party.”

The rest of the scribbled letters on pages from a notebook strike a similar message of their love for parents and assurances that they are as happy as circumstances permit.

“Don’t worry, I miss you all – grandpa, aunty, dad, mom and Nong [his brother or sister]. I love you all. I am happy, the SEAL team is taking care of us very well. Love you all.”

Another pleads to his teacher not to be given too much homework when he is rescued.

In possibly the bravest message from a 14-year-old boy: “I love you mum and dad, please don’t worry, I can take care of myself.”

The messages of courage and optimism came after parents sent their own messages of support via the constant shuttle of rescue divers making the four-hour trip to and from the boys’ refuge.

Governor Narongsak said the boys were still healthy and had practised wearing diving masks and breathing apparatus in preparation for their long and arduous journey back to the light of day.

If heavy rains returned and the massive battery of pumps could not handle the inflow, he said, tough decisions would need to be made.

Thai officials had been leaning in their public statements towards a quick underwater evacuation because of fear that access to the cave could soon close again because of seasonal monsoon rains expected this weekend.

However, cave rescue specialists have cautioned against that approach except as a last resort because of the dangers it poses.

A senior army commander, Major General Chalongchai Chaiyakam, said the most pressing mission is the oxygen line. It is tied to a telephone line to provide a channel of communication for the kids, who are stuck deep in the complex but are being looked after by four SEALs, including a medic.

The boys and their 25-year-old coach went exploring in the cave after a soccer game on June 23.

Monsoon flooding cut off their escape and prevented rescuers from finding them for almost 10 days as the only way to reach them was by navigating dark and tight passageways filled with muddy water and strong currents.

The death of former Thai navy SEAL Saman Gunan underscored those risks. The diver, the first fatality of the rescue effort, was working in a volunteer capacity and died during an overnight mission on Thursday in which he was placing air canisters along the route divers use to reach the children, General Arpakorn said.

The strategically placed canisters allow divers to stay underwater for longer during what is about a five-hour trip to reach the stranded team.

While underwater, the rescuer passed out and efforts to resuscitate him failed, General Arpakorn said.

Some officials said his collapse was due to his oxygen supply running out but the cause of his collapse was not confirmed.

-with agencies