Bernie Monk, the father of one of the 29 men killed when Pike River mine exploded, has entered the mine for the first time.

The father of one of the 29 men killed when Pike River mine exploded says it was "bloody freezing" when he went into the mine for the first time.

On November 19, 2010, a methane blast at the West Coast mine trapped and killed the workers inside, where they remain today.

Bernie Monk, whose son Michael died in the disaster, entered the mine on Thursday last week with Newshub journalist Patrick Gower.

CHECKPOINT/RNZ The Pike River Mine will be treated as a "crime scene" when re-entry finally occurs, the government says.

It was the closest he'd been to his son in eight years, Monk said.

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He took time to think about his son and the other 28 men still in the mine but the experience wasn't as moving as he expected, he said.

SUPPLIED Pike River re-entry minister Andrew Little at the portal of the Pike River mine in April.

"Going in wasn't as emotional as I thought it was going to be," he said.

"It didn't achieve much for me. You don't move on, you move forward."

He entered the mine because he wanted "to show the country that the families are prepared to go in", he said.

JOHN KIRK-ANDERSON/STUFF Bernie Monk, whose son Michael, 23, died in the disaster.

When he entered the portal it was 96.5 per cent methane beyond the 30m seal. The agency planned to purge the mine of methane using nitrogen and then allow fresh air in to the end of the drift, or mine access tunnel.

"It's bloody freezing in there," Monk said. "You can see the icicles on the roof, that's how cold it is."

The Pike River Agency had allowed the families access to the mine portal and several had already been into the mine drift in April including Pike Family representatives Anna Osborne and Sonya Rockhouse.

JONATHAN MARSHALL All 12 charges laid against former Pike River Coal chief executive Peter Whittall were dropped in 2013.

Monk and the majority of the families of the 29 men have been fighting for the mine drift to be recovered and accountability for the disaster.

Several years ago, Mines Rescue went up to 300 metres and put in a seal at 170m and 30m. Monk said he wanted to know who told them to stop at 300m.

"It should have been done seven years ago. I am challenging the law makers that you can not kill 29 men in the workplace and have no one brought to account," Monk said.

He had been to the portal several times before for anniversaries, when Solid Energy owned the mine, but was never allowed in.

Solid Energy kept the access road locked and "treated the families like criminals" when they began a protest against permanently sealing the mine in 2016, he said.

Newshub journalist Patrick Gower said on the AM Show on Tuesday a recovery team and Monk entered the portal and said it was"an incredibly emotional moment to be there".

"For me personally it was one of the most incredible things I've ever seen to see a father who has fought so hard to be so close to his son."

Monk had touched and gripped the wall as they entered the portal, he said.

The mine was deemed too dangerous to re-enter by the National Government and Solid Energy, which bought the mine after the disaster but technical experts are working on a plan to reenter the 2.3-kilometre access tunnel (or drift) to recover bodies and gather any evidence to find out how the explosion happened. Re-entry could start at the end of 2018.

The previous Government also said the mine could not be re-entered due to health and safety legislation brought in as a result of the Pike River disaster.

National Party spokesman for Pike River re-entry Chris Finlayson earlier said the decision not to re-enter the mine was based on the advice of Solid Energy that while manned re-entry was technically possible, it could not be done safely without putting lives at risk.

"We were not willing to take that risk."

Monk, who has laboured on behalf of some of the families, earlier said he had been ignored and "fobbed off" in his fight for justice but always knew police would "turn up back on the doorstep".

Police Commissioner Mike Bush met with families for the first time since police closed the case in 2013 to "express police support for the re-entry planning".

Monk said it was yet to be seen whether police claims that they were open to laying new criminal charges were legitimate.

In 2013, all 12 charges laid against former Pike River Coal boss Peter Whittall were dropped, and the families were told there was not enough evidence to pursue manslaughter charges, but in June the country's top police officers prepared to open a new investigation explosion.

The new investigation was reliant on access being gained to the mine's access tunnel or drift.

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