A New Zealand Police communications manager discussed the temperature variations with ILN yesterday.

She said the readings from the slimline hole, near the “shaft-end of the operation”, revealed temperatures in the low 30s (degrees Celsius) but also registered increases up to more than 100 degrees in “virtually the same day”

The spokesperson added that the slimline hole did not necessarily provide a good idea of what was happening in the mine workings.

“We're working to get more drilling done and also working towards grouting the area around the slimline shaft,” operation commander superintendent Gary Knowles said yesterday afternoon.

But further drilling requires helicopter support because of the mountainous terrain and the West Coast is known for its high rainfall.

Grouting work on the slimline hole is also dependent on the weather.

A recent borehole completed just before Christmas has not proven to be “very useful” according to the Police spokesperson.

She confirmed that both the GAG jet engine and Air Liquide’s mobile Floxal nitrogen generator are both being used together to inert the atmosphere underground.

While she did not provide methane levels, she said gas was still a big issue.

“Every time the GAG has been turned off the methane just started ticking up again fairly quickly.”

The Floxal unit is a smaller 500 cubic metre per hour system while the 2000cm/h systems are used in Australian longwall mines.