Pike River mine disaster
Police are re-evaluating how they can recover the bodies of 29 men still underground ten days after they were trapped by an explosion at Pike River Mine, after a fourth and violent explosion earlier today sparked a coal fire in the mine.
Inspector Mark Harrison said the explosion was fuelled by methane, as the previous three have been.
"However, it literally sparked a coal fire in the mine. The fire is visible from the air above the ventilation shaft which was further damaged during the latest explosion."
Large amounts of smoke and flames are coming from the mine and chief executive Peter Whittall says it may have to be temporarily sealed.
"There is quite a large amount of smoke coming out of the mine. This smoke has changed, it's no longer a gas fire, it's obviously now a coal fire," Mr Whittall told a press conference at 7pm.
"Where that coal fire is or how big it is, we don't know."
The worst-case scenario is that the actual coal seam would start to burn. A gas fire was pretty easy to put out, but a coal fire in a seam would be a "very different beast", he said.
Operators were still hoping to deploy the Gorniczy Agregat Gasniczy (GAG) jet engine to force inert gases into the mine and smother the fire, but were now having to consider temporarily sealing the mine, to starve it of oxygen.
However, this was not the preferred option.
The risk assessment team members were still considering the best option.
"We've had a lot of explosions underground, so we've obviously dislodged a lot of coal so there's (been) a lot of fuel in the mine to burn."
Mr Whittall told reporters he thought today's explosion, at 1.55pm, would have been stronger than the previous three. Unlike the previous ones, it went straight up the mine shaft "quite violently", rather than out the entrance tunnel.
It was the fourth explosion in the mine since a blast on November 19 trapped 29 men in the mine, and another blast on Wednesday dashed any hopes that they might be found alive.
Responding to a reporter's question, Inspector Harrison said that the bodies may no longer be "intact".
Vegetation by the mine shaft had caught fire, but has been extinguished.
Mr Harrison said the best options were not yet clear, but the safest course method of recovery would be decided "as soon as we are able".
He said up to 180 people from Pike River Coal, Red Cross, Ambulance Services, Mines Rescue experts, the Defence Force, Fire Service and others had been working near the mine since it first exploded on November 19.
There were no injuries from today's explosion and people working near the entrance to the mine were moved away from the area for their safety.
Superintendent Dave Cliff said the latest explosion demonstrated the volatility of the environment surrounding the mine.
"Our focus continues to be on the safety of those people working at the mine site and the recovery team.
"We are doing all we can to progress the recovery operation, however the explosion reinforces the risks involved in working in this environment and the requirement to put people's safety first."