The lawyer for Pike River families is now confident that police have gathered enough evidence to pursue a manslaughter prosecution against mine bosses, more than a decade after the disaster. 

Police yesterday confirmed that a criminal probe is ongoing while final images taken during a borehole drilling project captured evidence of further human remains deep inside the West Coast coalmine that exploded on November 19, 2010 and killed 29 men. 

The families' lawyer Nigel Hampton QC told RNZ's Morning Report today that the police's "quite rigorous and disciplined" investigation has given him confidence that they're on track. 

"I think it's all done with a view to excluding certain conjecturable causes – what might be seen as causes of this explosion," he said. 

Nine years ago, police reached a view that they had sufficient evidence of gross negligence to bring a case of criminal nuisance against certain management, if not the directorship of the Pike River mine, Hampton said, in terms of the setting up and running of the mine. 

The "missing piece" was the cause of the explosion that resulted in so many deaths, Hampton said. 

"The process that's been gone through in the last three years or so has really been to eliminate, I believe, conjectural causes and come back to a proposition that there is no other plausible explanation but that this explosion was caused directly as a direct result of the gross management/directorship of the mine," Hampton told RNZ. 

Nigel Hampton QC. Photo / File 

Technology has improved over last decade to provide clearer and more detailed images and the evidence obtained by police has now given Hampton confidence to tell families that they are finally on course to "consider that there will be a prosecution for manslaughter taken". 

Asked if he was concerned over the length of time it's taken to reach this point, Hampton responded: "I would rather they took time and do it methodically, thoroughly, and hopefully foolproofly. So, time, in that sense, is not a factor against what is occurring – it's in favour in terms of the solidity of the investigation." 

Families of the 29 men who died in the Pike River disaster were yesterday told that the latest images taken inside the mine have been reviewed by pathologists and show two sets of human remains. 

Police say that one of those images was identified as human remains - and the families were told - back in early 2011. 

The images were taken in the roadway leading to the Goaf area where it is believed that three men had been working. 

Detective Superintendent Peter Read at November's press conference in Christchurch announcing bodies had been found at Pike River. Photo / George Heard 

The discovery means that eight sets of human remains have now been captured in imaging taken during borehole drilling. 

"As I've noted previously, the search for answers over the last 11 years has been a long and painful journey for the families of the 29 men lost at the mine," said Detective Superintendent Peter Read yesterday. 

"While the discovery of these eight sets of remains is significant, I'm very aware that it still leaves many unanswered questions for the men's loved ones, and my thoughts are with all of the families today." 

The redrilling of the borehole brings to an end the borehole drilling operation, which started in early 2019. 

The drilling operation has given police "valuable information to inform our investigation" into the underground activity that led to the first explosion, Read said. 

"On behalf of NZ Police, I would like to extend my sincere thanks all those who worked on and supported the drilling operation, including Pike River Recovery Agency staff, and other drilling and mining experts," he said. 

While the drilling operation has concluded, police yesterday confirmed that work on the criminal investigation is ongoing. 

Some of the Pike River families say the discovery is emotional but will help with closure for many. 

Anna Osborne, whose husband Milton died in the disaster, said although the find was not a surprise, it is still hard. 

"We've known for a long time there was at least one of our men under borehole 47, but that doesn't make coming back to it any easier," she said. 

"What is giving us some comfort is that now, as we get to the end of the project and the mine is sealed, we're getting real answers about what had happened there." 

Minister Responsible for Pike River Re-entry Andrew Little, in November, would not be drawn on whether a prosecution was imminent with the police investigation ongoing. 

The Pike River Recovery Agency (PRRA) completed its $50m re-entry of the mine's access tunnel to try and recover remains and find any forensic clues last year. 

It had been due to permanently seal the mine while police were partway through their borehole investigations. 

Pike River Mine family members Anna Osborne, left, and Sonya Rockhouse are among those still pushing for a criminal prosecution. Photo / NZME 

But some Pike River families who lost loved ones, and had fought for years to try and get authorities to try and find their bodies, launched legal action to try and stop it from happening. 

On Friday, November 19, 2010, about 3.44pm, an explosion ripped through the Pike River underground coal mine, followed by subsequent explosions. Two men made it out alive but another 29 were unaccounted for. 

The Royal Commission on the Pike River Coal Mine tragedy found that the "immediate cause of the first explosion was the ignition of a substantial volume of methane gas", but could only speculate on what might have triggered ignition. 

"The mine was new and the owner, Pike River Coal Ltd (Pike), had not completed the systems and infrastructure necessary to safely produce coal. Its health and safety systems were inadequate," the commission's report said. 

WorkSafe laid charges against former Pike River boss Peter Whittall in 2013, but the case was dropped after a $3.4 million settlement was paid – a deal the Supreme Court later said was unlawful. 

The money was split between the two survivors and the families of the 29 missing, a total of $110,000 for each man who had been down the mine that day 

Australian company VLI Drilling, which employed three of the men who died, also pleaded guilty to health and safety charges and was fined $46,800.