Police say putting a cap on the Pike River Coal mine could cause further explosions.
“Despite the GAG operating for more than a week now we know there is till oxygen getting into the mine and the risk of further combustion still exists,” said Tasman District Commander Superintendent Gary Knowles.
He said conditions at the mine are still dangerous, with temperatures inside reaching 600 degrees Celsius, and capping the mine could cause the GAG machine to stall, leading experts to predict it could cause further explosions.
"Despite no flames being visible at the vent there is still a significant quantity of gas escaping which poses a huge risk to helicopters flying overhead," Knowles said.
He said recovery attempts are still a long way off, and the next phase involves using nitrogen-generating equipment to pump gas into the mine to lower temperatures.
The machines for such a process are available in New Zealand and Australia, but will only be used after expert assessments.
"The situation remains the same. All of the evidence to hand confirms this would be an extremely high-risk operation."