Some of the families of the men who died at the Pike River Mine are hopeful former mine boss Peter Whittall could still face manslaughter charges over the deaths of their loved ones.

"I'd like to see even up to the stage of manslaughter here," said Bernie Monk, whose son Michael died in the 2010 explosion.

"Twenty-nine men went to work one day. The [Royal] Commission has already said the mine was in a dangerous situation," he said.

Pike River Coal knew that the mine's atmosphere was in the explosive range for a number of days, he said. "They continuously let our men go into that mine and eventually it did blow up.

Advertisement

"They murdered those men in that mine," Monk said.

Sonya Rockhouse, whose son Ben died in the mine, said she was unable to say publicly what she wanted to say to Whittall.

"I'm actually speechless when it comes to what to say to him. If I saw him face to face, I'd have one question for him. Why?

"Why did he not tell us the truth right from the start. He knew, lots of people knew and they weren't honest with us. They didn't try, they didn't do anything.

"Why did he just walk away and just let 29 men remain down the mine," Rockhouse said.

"Not only after the explosion but before the explosion, he let them down right from the very beginning. He should have built a mine that was going to be safe for men to go in and work in every day and he didn't. "

She hoped there would be criminal charges.

"This is what we have been asking for all the way along."

Police have been involved in planning for any re-entry to the drift since the middle of this year so they can prepare for any forensic examination and victim identification.

In the aftermath of the disaster, WorkSafe put together a case that would have brought 12 charges against Whittall, who was the chief executive of Pike River Coal.

The case was dropped after Whittall agreed to pay $3.41 million to the families of the men killed but the Supreme Court later ruled that was unlawful, and effectively a payment to avoid prosecution.

Pike River Re-entry Minister Andrew Little said today that prosecutions were a matter for police and other agencies such as WorkSafe.

"Police closed their investigation, but not the file, in 2013, so investigations into potential criminal wrong-doing are still open for the police," he said.

Little said Whittall could not be re-charged with offences under the Health and Safety Act that had already been dealt with.

Police Commissioner Mike Bush, who was at today's announcement, did not rule out manslaughter charges.

It was now a criminal investigation and it was important to follow the evidence, he said.

"Our case is open and everything will be based on evidence. The purpose of us being involved here is, if it's safe, to ensure that we take advantage of any opportunities to examine forensic evidence."

While he would not be drawn whether Whittall might face manslaughter charges, Bush said: "We've got a very open mind on this investigation."

Bush would not say whether police had spoken to Whittall recently or whether they intended to speak to him or other senior staff of Pike River Coal.

Assistant Commissioner Richard Chambers, who accompanied Bush today, would also not say whether police had spoken to Whittall.

"Our investigation is open so we're not about to start discussing it ... it's far too early. We have a very open mind and we're working very closely with the agency."

The Herald attempted to speak to Whittall today but staff at the rest home where he works in Wollongong, Australia, said he was unavailable.

Whittall, who left New Zealand in 2014 and is married to Pike River Coal's former financial controller Angela Horne, told Fairfax in an interview in August this year that he felt no guilt.

"Do I feel guilt? No. It is human nature to blame someone," he said.

"To this day nobody has told me what happened. Nobody knows, that's why the families want to go underground. People have theories but nobody actually knows," Whittall said.

"It was a terrible tragedy but I would defend my position because I feel I always put the interests of my staff and workforce before everything," he told Fairfax.