Mae Sai: Rescue divers were making progress through a key passageway inside the flooded mountain cave in northern Thailand on Monday where 12 boys and their soccer coach have been missing for more than a week.

Thai navy SEALs said in a Facebook post early on Monday that divers since Sunday night had reached a bend where the kilometre-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.

The boys, aged 11 to 16, and their 25-year-old coach entered Tham Luang Nang Non cave in Chiang Rai province on June 23. Heavy rains that flooded key passages are believed to have trapped the soccer players and have thwarted the search for them.

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.

"I hope that today we will continue to have another good day. It will be even better if everything else could run smoothly," Chiang Rai Gov. Narongsak Osatanakorn told reporters Monday.