MAE SAI, Thailand -- Rescue divers spent much of Monday making preparations for what is hoped will be a final push in their search for 12 boys and their soccer coach who have been missing for more than a week in a cave in northern Thailand. Chiang Rai provincial Gov. Narongsak Osatanakorn said the divers concentrated on securing a rope line and placing oxygen tanks along the narrow passageway that they think will lead them to the boys, aged 11 to 16, and their 25-year-old coach, who disappeared when flooding trapped them after entering the Tham Luang Nang Non cave on June 23.

Thai navy SEAL divers and rescue workers from other countries made initial progress through the narrow passageway early Monday after passing through a key chamber on Sunday whose high, murky waters had previously blocked their progress.

Narongsak said the passageway the divers were making their way through goes upward in some places and downward in others and is extremely narrow, making it difficult for divers with all their gear to fit through.

Divers have been stymied again and again by muddy water rising filing sections of the cave and forcing them to withdraw for safety reasons. When water levels dropped Sunday, the divers went forward with a more methodical approach, deploying a rope line and extra oxygen supplies along the way.

The SEALs' Facebook page said that since Sunday night, the divers had reached a bend where the half-mile-long passage splits in two directions. The divers are aiming for a sandy chamber on higher ground in the cave, where they believe the group would be safe.

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On Monday, they were again employing the methodical, safety-first approach to make it through the passageway.

Narongsak explained Monday that fixing rope lines and deploying oxygen tanks along their route will allow the divers to operate.

Public anticipation for a rescue has been high since Sunday, but officials have avoided setting a timetable for the search and rescue operation. They publicly remain optimistic.

"In theory, human beings can last 30 days (without food)," Narongsak told reporters. "We hope and believe that is the case. We all still have hope."

Rescue workers carry heavy water pumping equipment into Tham Luang Nang Non cave, July 1, 2018 in Chiang Rai, Thailand. Getty

He said it was expected that in their condition, the boys would at first not be able to move their limbs, but that medical teams would initially treat them in place. He said the diving teams included doctors who were already inside the cave.

In addition to the divers, teams have been working to pump out water as well as divert groundwater. Other efforts have focused on finding shafts on the mountainside that might serve as a back door to the blocked-off areas where the missing may be sheltering.

Teams have been combing the mountainside looking for fissure that might lead to such shafts. Several have been found and explorers have been able to descend into some, but so far it is not clear whether they lead to anywhere useful.

Narongsak said they were focusing Monday on six shafts, up from two the day before. Authorities also used helicopters to place heavy equipment such as backhoes and drilling machinery on the mountainside. The plan is to try to widen some of those shafts.

Experts in cave rescues from around the world continued to gather at the site. An official Australian group has now followed a U.S. military team, British cave experts, Chinese lifesaving responders and several other volunteer groups from various countries.

"These are challenging conditions and there's a lot of consideration for safety as well as, the environment outside is contributing to the environment inside," said U.S. Air Force Capt. Jessica Tait, part of a 30-strong U.S. military team assisting in the search operation, referring to the rain that has been flooding the cave. "So I'd say, yeah, it's an accurate statement that it's challenging."