Chiang Rai: British cave expert Vernon Unsworth has managed to reach Nern Nom Sao, a cave chamber where the 12 young footballers and their coach were trapped, as part of efforts to retrieve a large quantity of rescue equipment.
So far, only some equipment, notably dozens of heavy water pumps, have been recovered.
The equipment was left behind when massive flooding in Tham Luang forced rescuers to only extract the under-16 football team and their coach from the cave complex in June and July last year.
Authorities revisited the cave in mid-January only to turn back due to floodwater.
The retrieval effort resumed earlier this month but attempts to reach Nern Nom Sao were not successful until Mr Unsworth's effort.
His team ventured 2.5 kilometres into the dark narrow cave complex until they reached Sam Yaek, a fork in the cave.
The team managed to break through a "wall of sand" which had hindered their progress toward Nern Nom Sao, which is now dry.
A large amount of rescue equipment, including air tanks, were left buried under the sand, according to Mr Unsworth's team.
The retrieval team, led by Chiang Rai-based Disaster Prevention and Mitigation Regional Centre 15, will need to extend its four-day operation, which was earlier scheduled to be completed yesterday.
Centre director Phaitun Nakthae has asked Chiang Rai governor to give the team another two days, or until tomorrow.
While authorities have managed to retrieve some of the equipment, nearly 10km of electrical cord still remains inside, he said.
The National Park, Wildlife and Plant Conservation Department, which had closed Tham Luang-Khun Nam Nang Non Forest Park to the public between Tuesday and yesterday, insisted it will not extend the closure.
People can visit the area from today, forest park chief Kawi Prasomphon said.
