Two families of Pike River mine victims say they have been told by police that charges over the disaster are likely.
It comes as the deadline for the completion of the forensic investigation was pushed out to October and more money was put in to drill six boreholes to enable police to see beyond the roof fall currently blocking their way.
Dean Dunbar, whose son Joseph died just one day after his 17th birthday, said the news that charges were likely was broken to him four weeks ago by the inquiry head, detective superintendent Peter Reid and assistant commissioner Sue Schwalger.
"Peter suggested that serious criminal charges will be laid, that people will be extradited from other countries. It's going to take a lot of time. But at the end of the day, no matter what, it will be crown law that makes that decision," Dunbar said.
Bernie Monk, whose son Michael died in the mine, said he was also told by Reid about a month ago that charges were likely.
"They led us to believe, they didn't say the charges will be made, but [said] it's very likely that charges will be made - they didn't guarantee us but they said it looks very like it," Monk said.
However, neither man held out much hope that police would be successful in achieving justice for their boys.
Dunbar said Reid was in charge of the investigation the first time around in 2013 when it was decided there was insufficient evidence to lay criminal charges.
That was followed soon after by WorkSafe's decision to drop 12 health and safety charges against mine boss Peter Whittall in return for a $3 million payout - a decision that was subsequently found to be unlawful.
"I'm sure if the Department of Labour wasn't so negligent and didn't have the systemic problems that it had, as far as I'm concerned still has, and the rescue and recovery didn't turn to custard and go so bad, perhaps it wouldn't have got so political," Dunbar said.
Monk thought there was a 50-50 chance of a prosecution actually happening this time around.
He and Dunbar, with the help of various experts, had been able to find out more about the cause of the disaster in 18 months than the police were able to in three years, and he had very little faith in them, Monk said.
"We're going down the same road as the CTV building. We're going down the same road because the police that investigated the CTV building, a lot of those police are the same police that are doing Pike River."
Moving beyond the roof fall to the nearby ventilation fan - thought to be a potential ignition source - was vital, he said.
"If I was a defence lawyer that'd be the first thing I would bring in my defence, wouldn't you? I mean the old scenario, beyond reasonable doubt, and you never looked at one of the main things which is the fan. It's a major, major."
Approached for comment, the police said no decision had been made about laying charges.
One thing was certain, however, and that was their investigation was taking longer than first expected.
Pike River Recovery Agency chief executive Dave Gawn - who just before Christmas was predicting the mine recovery and forensic investigation would be completed by June - now said that would not happen until October.
Part of the delay was due to six boreholes the police now wanted to drill so they could send cameras down into the main workings of the mine.
Dawn would not be drawn on whether the agency would now have to go over its $50m budget.
"We're working through issues around managing the cost pressures and it's still a work in progress," he said.
Meanwhile, Monk and Dunbar said they would keep the pressure on the police to act in a transparent way with the families and ensure that no stone was left unturned in their battle for justice for the 29 men.