More than 100 chimneys are being drilled into the mountainside in a frantic bid to reach a Thai youth football team trapped in a cave complex below, the head of the rescue mission said on Saturday.

The unprecedented rescue effort is attempting to establish new ways to extract the boys from above, if the underground chambers flood and it is deemed too risky to evacuate the team by diving out through the submerged passageways.

“Some (of the chimneys) are as deep as 400 metres... But they still cannot find their location yet,” Narongsak Osottanakorn told reporters, adding the mission lacked the technology “to pinpoint where they are staying”.

“We estimate that (they) are 600 metres down, but we don’t know the (exact) target,” he said.

Over 100 ‘chimneys’ drilled into mountain