State-owned coal producer Solid Energy, which acquired the sealed mine from the receiver last year, said air force and army personnel were removing structures such as fan ducting and generator sets at the top of the mine’s burnt ventilation shaft.

This paves the way for starting phase one in this area, inertising the remaining 50-60m of the shaft to “ensure full control of the mine atmosphere”.

“We are pleased to have reached this start point and to have the support of the New Zealand Defence Force in clearing the site,” Solid chairman Mark Ford said.

“While Solid Energy is managing the project, it is very much a collaborative effort, with funding from the Government and the expertise of many individuals and organisations who have come together to plan it and carry it out safely.”

Air Component Commander Mike Yardley said it was the first time an NH90 helicopter was used to support another government agency.

“The NH90 has twice the lifting capacity of civilian helicopters available to Solid Energy and therefore we are pleased to be able to provide assistance for this important task,” Air Commodore Yardley said.

The NZ government approved the $NZ7.2 million re-entry project more than a month ago. The goal is to send mine rescue and other experts 2.3km into the drift access tunnel and close to the debris blockage caused by a roof fall.

The bodies are expected to be past this obstacle and into the various roadways and mine working areas, but reaching this point could open up more possibilities.

Prior stages of the operation will plug the ventilation shaft and drill new boreholes for surveillance and gas drainage. A seal created with ROCSIL expanding foam will be made close to the rockfall blockage. The rest of the access drift to the surface will be pumped full of nitrogen to inertise the atmosphere.