Officials say they are not ready to dive out yet following the death of a former Thai Navy SEAL who ran out of oxygen during the rescue mission.
Katadzic has not dived the final kilometre to where the boys are stranded on a muddy bank, the most unsafe part of the dive, during which rescuers have to hold their oxygen tanks in front of them to squeeze through submerged holes.
"Some (of the chimneys) are as deep as 400 metres - but they still can not find their location yet", Narongsak Osottanakorn told reporters, adding the mission lacked the technology "to pinpoint where they are staying".
"If there's heavy rain we will try to bring them out", he said.
Officials also said Friday that water levels continue to fall in the cave and that they have succeeded in getting an oxygen pipeline to the section of the cave where the boys are stranded and where the supply was running dangerously low.
Exploring a cave system after soccer practice, the boys wandered far into the Tham Luang caves before being trapped in a flash flood.
The football coach trapped in a Thai cave with 12 boys has apologised to their parents as the youngsters sent out heartfelt notes describing their plight.
Handwritten messages from the 12 boys and their soccer coach trapped in a cave in northern Thailand for nearly two weeks have made the long journey from their cavern confines to the world waiting anxiously for them outside.
"Dear all kids' parents, now all of them are fine, the rescue team is treating us well. I promise to take the very best care of the kids", he said in a note given to a diver on Friday and published on the Thai Navy SEAL Facebook page on Saturday. I would like to thank you for all the moral support.
A mother of one of the 12 missing boys, displays an image "Dom" (holding torch) with football coach Ekkapol Chantawong (R).
"The kids said 'don't worry, ' everyone is strong, they have a long list of food they want to eat when they get outside", a Thai Navy SEAL wrote on the first of a small collection of mud-stained papers delivered by a diver.
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Italy couldn't score in 180 minutes in the qualifying play-offs. " Sweden don't have a Kane, Sterling or a Neymar". The coach plays to the strengths of the players and if you underestimate them then you are in trouble.
The football coach's message is the first time he has spoken publicly after facing criticism for agreeing to take the young boys into the cave during the monsoon season.
The group entered the cave on 23 June and got trapped as floodwaters tore in. Don't be too anxious.
Although he had left the navy, Saman, a triathlete, felt a calling to join the rescue effort.
Saman Gunan was considered a highly trained diver.
He has since been hailed a hero for his efforts, with Thailand's Prime Minister promising that he did not die in vain.
Rescue workers work near the Tham Luang cave complex in the northern province of Chiang Rai, Thailand, July 7, 2018.
Late Friday, Thai officials were still trying to come up with a workable extraction plan for the group trapped for almost two weeks deep inside the cavern, stoking fears that all available options remain too risky.
"We are afraid of the weather and the oxygen levels in the cave but we have to try and minimise the risk", he added, the publication reports.
Narongsak Osatanakorn confirmed that the boys - who do not know how to swim - have been taught the basics of diving: including using the oxygen masks and submerging into the water.
Cave rescue experts have said it could be safest to simply supply the boys where they are, and wait for the flooding to subside.