Police have been accused of endangering potential survivors and jeopardising a body recovery operation by refusing to seal the explosion-hit Pike River mine.

Assistant police commissioner Grant Nicholls is under cross-examination at a Royal Commission of Inquiry into the deaths of 29 men in the Pike River mine this morning.

Solid Energy counsel Craig Stevens asked why police had not sealed the mine, on the advice of New Zealand Mines Rescue and Solid Energy workers.

Experts had suggested sealing the mine portal while maintaining a flow of compressed air to a fresh air base where survivors could have been gathered, Mr Stevens said.

"You could have sealed the mine but still preserved life in it. But by not sealing it the probable second explosion would almost certainly kill any survivors."

Mr Stevens presented police documents showing a second blast was expected from the time of the first explosion at the mine.

He said sealing the mine could have prevented the devastating November 24 explosion which erased any hope of finding survivors.

The explosion sparked a coal fire and caused a roof collapse in the mine, making a body recovery operation more difficult.

Mr Nicholls said it was his understanding sealing the mine would have extinguished any hope for survivors.

He did not want to make the decision to seal until any hope of finding people alive was ruled out.

"I think by sealing it you would have definitely created a situation where life was no longer a viable option."

He said New Zealand Mines Rescue and other mining experts had been consulted throughout the rescue and recovery operation at Pike River.

Mr Stevens also asked about frustration at the time it took for the police and Department of Labour to make key decisions during the rescue and recovery operation.

He pointed to one team that threatened to leave Pike River over delays getting approval to drill a bore hole.

Mr Nicholls said there had been some frustration during the operation.

First explosion deadly - experts

Earlier, Mr Nicholls admitted he had not read New Zealand Mines Rescue documents claiming no-one survived the first explosion at the Pike River mine.

Under questioning New Zealand Mines Rescue counsel Garth Gallaway, he said police commanders had not read expert reports on survivability at the mine.

The reports from New Zealand Mines Rescue and New South Wales mines rescue said the 29 trapped miners would most likely have died almost instantly after the first explosion on November 19.

If they survived the blast, the toxic atmosphere inside the mine would have killed them within minutes, the reports said.

Mr Gallaway said those findings never made it through to police because of the way communications were structured during the rescue and recovery operation.

"[I am asking] whether you knew the view of the two expert agencies and the answer is no," he said.

"That is correct," said Mr Nicholls.

Mr Gallaway presented a report issued on November 20 showing the environment inside the mine was "unlivable" due to the level of carbon dioxide in its atmosphere.

He cited internal advice issued to police national headquarters on November 21 which said operations at the mine were moving from rescue to recovery.

The bodies of the trapped miners could have been preserved and recovered if police had ruled out the possibility of survival earlier, Mr Gallaway claimed.

"If you'd established there would be no survivors the mine could have been sealed, thus preventing any further explosions, thus the miners would be preserved."

Mr Nicholls said police were considering a wide range of expert advice on whether there were survivors inside the Pike River mine.

He said those in charge of the recovery were given hope by the fact mine workers Daniel Rockhouse and Russell Smith had survived the first explosion.

"Two people survived this disaster. Those two people were rendered unconscious.

Brought themselves to... Two survived. I think that's a really critical piece of information."

Pike River chief executive Peter Whittall had told police the men may have been waiting for rescue at a fresh air base in the mine, Mr Nicholls said.

"There was a lot of hope. I've explained that. And there was a lot of information to consider. To look at information as an abstract is not... the reality of the operating environment."

"The issue of survivability could not be dealt with quickly."

Mr Gallaway said mines rescue experts would disagree with his view.

He criticised police for relying on the advice of Pike River company bosses over that of mines rescuers.

Mines rescue not consulted on recovery

It was revealed police commanders did not consult expert mines rescuers on the risks of recovering men trapped inside the explosion-hit Pike River mine.

Mr Nicholls admitted failings in the consultation between police and New Zealand Mines Rescue during the rescue and recovery operation.

Under questioning from New Zealand Mines Rescue counsel Garth Gallaway, he admitted no-one at police headquarters asked mines rescuers to review risk assessments of the Pike River mine.

He said the decisions on the risks of rescue and recovery operations at the mine were made with the input of a panel of experts including the Fire Service and St John's Ambulance.

Mr Gallaway said the fact no mines rescue service personnel were consulted "highlights a significant problem in the risk assessment".

Mr Nicholls said decision making processes and structure would be changed if another mine disaster occurred, but was not a major failure.

"I don't agree that it highlights a significant problem. It highlights an issue."

Police brought order to chaos

Earlier, Mr Nicholls revealed no other agencies were consulted when police took control at the Pike River mine site after the first explosion on November 19.

"Order had to be brought to a very chaotic situation. So this was a period where decisive action had to be taken."

Other agencies, including New Zealand Mines Rescue, would be consulted before establishing a command structure to respond to any future mine disaster, Mr Nicholls said.

He also faced questions on the chain of command during the rescue and recovery operation at Pike River.

Mr Gallaway said most decisions were made by police national headquarters, on the basis of advice from police staff in Greymouth.

"It was police, police and up to police... That's how all communication was done."

Mr Nicholls said police in Greymouth had consulted with experts including New Zealand Mines Rescue service personnel before issuing reports to national headquarters.

- Herald Online staff