Chanting monks in orange robes prayed alongside distraught relatives outside a flooded cave in northern Thailand where 12 children and their football coach have been trapped for days.
Rescuers battled heavy rain as they struggled to drain the flooded tunnels in the Tham Luang cave where the youngsters, aged 11 to 16, and their coach have been stuck since Saturday.
Three British cave-divers who have previously explored the site arrived in Thailand today to join about 1,000 soldiers, navy SEAL divers, police and park rangers at the mud-slicked site in the northern province of Chiang Rai.
Officials shipped in several high-pressure water pumps overnight to help drain the waterlogged chambers of the cave near the Laos and Myanmar borders, which is several kilometres long. It was a losing battle as rain kept falling for most of the day, but by evening one of the largest pumps was set up and operating.
Murky water and limited oxygen inside the cave also proved difficult for the 200 rescuers inside.
Thailand's SEAL unit said on its Facebook page that water levels rose 15 centimetres (six inches) overnight and that a third chamber of the complex cave network -- believed to be several kilometres long -- was flooded.
As the desperate search for the missing boys entered its fifth night, officials said they were still sure they would find them.
"We are confident the children are still alive. They have food, they are skilful, we are confident they are safe," Interior Minister Anupong Paojinda told reporters. "We need to do everything to reach these children."