The Thai Water Well Association on Friday added its equipment to the battery of well diggers already in operation in the search for 12 footballers and their assistant coach lost in a flooded Chiang Rai cave since Saturday.
There were five mobile well-drilling units on the scene on Friday as officials selected optimum places to drill for subterranean watercourses to drain the cave faster.
But the underground water channels proved elusive. A vertical shaft dug Friday morning not far from an angled 70-metre hole excavated the previous day also turned up nothing.
Chiang Rai Governor Narongsak Osottanakorn said on Thursday it was not known how much floodwater there was in the cave because it was entering via multiple small holes throughout the massive cavern.
Water was being pumped out around the clock, he said, and in greater quantity thanks to a shift from textile pump tubes to PVC tubes.
The floodwater level at the cave entrance had dropped three centimetres by Thursday, Narongsak said.