Another unit of Royal Thai Navy Seals was expected to arrive yesterday with more rescue equipment for the team of missing young footballers and their coach.
They will help pump water out of the cave and comb through surrounding areas looking for more shafts leading down into the cave.
Theeraphong Burirak, director of the Chiang Mai-based Provincial Electricity Authority Region 1 (North), said 13,700 metres of waterproof electrical wire had been delivered to the site to extend the 4,000 metres of wiring already in place and enable electricity to be supplied deeper inside the cave.
Meanwhile, US rescuers were deploying ultrasonic sensors to be used for underwater navigation in the turbid water.
Infrared body heat detectors, to help locate those missing, and diver propulsion vehicles were also being employed.
The young students, aged 11-16, were led into the cave system by their 26-year-old coach after practice on Saturday and have not been seen since.
It is believed they were trapped inside by rising flood water caused by heavy, continuing rain.
Their bicycles, shoes and backpacks were found close to the cave entrance.
A rescuer prepares to drill areas near a crevice as his team speed up operations to deliver food boxes via the crack to the 13 people believed to be stuck in the cave. Patipat Janthong
A number of the cave complex's underground passages were reportedly flooded with mud severely impairing visibility for divers.
Prime Minister Prayut Chan-o-cha paid a visit to the cave site yesterday to offer moral support to the rescue workers and pray for the safety of the team.
During the visit, Gen Prayut conveyed His Majesty's concerns to the families and workers and said the government would do all it could to help support the rescue mission.
Gen Prayut said the incident underlined the need for Thailand to raise its rescue operation standards.
The families of the missing were camping out in makeshift tents outside the cave, joined by throngs of reporters and photographers.
The operation involves hundreds of people from various agencies including the elite Navy Seal unit.
British divers and cave experts , US military personnel, and rescue teams from Laos have also joined rescue efforts.
Diverting water from the flooded cave remained a core mission while rescuers were seeking alternative ways of entering the cave.
So far the location of the missing group remains unknown but there is hope they may be waiting to be rescued at a chamber called " Pattaya Beach".
Meanwhile, the monastic community in Chiang Rai bought 11,000kg of pineapples from local farmers yesterday to give to the many rescue workers to help sustain them.
Phra Thamsenabodi, the abbot of Wat Phra That Doi Suthep in Chiang Mai, urged Chiang Rai governor Narongsak Osottanakorand and the rescue teams not to lose hope.
Udom Chuleewan, a school director in Songkhla, said 2,000 people took part in a mass prayer for the missing team.
"We really believe they will make it," he said.
