The group could be stuck in the cave "up to three or four months," Ben Reymenants, a locally based diving instructor who is assisting with the effort, told NBC News on Tuesday. Two Thai Navy doctors have volunteered to be "locked up" in the cave with the team, he added.
Two other complications: Heavy rains forecast for northern Thailand could exacerbate flooding in the cave, and the boys do not know how to swim.
“The water level in the cave is still very high, so we have to teach them how to swim to come out from there,” the provincial governor, Narongsak Osottanakorn, told reporters. “We will give them diver masks, but only the rescue teams can decide whether they can be brought out safely in this way."
The handful of rescuers who joined the group in the cave brought food and energy supplements, salt water solution, anti-inflammatory drugs and basic painkillers, he added.
"They are very weak and very skinny, and almost unable to walk," Reymenants said, "so that’s what they are working on now — to give them strength and get them back on their legs."
The schoolboys, ages 11 and 16, and their 25-year-old assistant coach set out on June 23 after a soccer game. What was supposed to be a trip to the Tham Luang Nang Non caves in Chiang Rai, a popular tourist attraction in the region, turned into an ordeal that has transfixed the country after rising waters trapped the group.
Rescue efforts were launched after parents reported the boys missing,but heavy rains hampered the work with muddy water filling the cave chambers and stopping the divers trying to find the group.
A six-mile labyrinth of caves and narrow passages runs under the mountainside, and the group is stuck in the middle, making access to the boys and coach difficult, Reymenants said.
Let our news meet your inbox. The news and stories that matters, delivered weekday mornings.
Given the complexity of the operation, the Thai-led multinational team of rescuers is currently assessing the safest way of extracting the group.
"They are looking at all the possible options because it's paramount that this is being done safely," said U.S. Air Force Capt. Jessica Tait, one of around 30 Air Force members who arrived last Thursday from their base in Okinawa, Japan, to assist the Thai government with the rescue.
With the cave complex still flooded, and thunderstorms expected to drench the region over the next week, reaching the boys is arduous and time consuming.
"From the operations center in the third chamber to where they were found, it takes about three hours to get there and three hours to come back," Thai Navy chief, Adm. Naris Pratoomsuwan, told reporters.
Although water pumps have been sucking water out of the caves, rescuers would prefer the group walk out rather than swim and dive through the flooded tunnels, a Thai Navy spokesman told NBC News.