The families of the Pike River Mine explosion victims want answers from police.
They claim police didn't effectively look at the black box, otherwise known as Scada data, beyond the first explosion.
Scada (Supervisory Control and Data Acquisition) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management.
Following the first, two miners made it out alive but the 29 others were trapped and on November 24, five days later, the second explosion was set off.
Ever since those who lost loved ones in 2010 disaster have been searching for answers to what happened between the two explosions.
After a long fight with police to try and prove the existence of a black box, police conceded one exists despite months of denial.
The families started asking questions to police about Scada data on November 15 last year, asking for the information.
Dean Dunbar and Bernie Monk allege police responded on March 11 and told them the black box did not exist beyond November 19, 2010, when the first explosion hit.
However, after contacting Dave Gawn, chief executive of the Pike River Recovery Agency, he told them information stretched right up until the second explosion.
Following the confirmation from Gawn, police fronted up and said they have Scada data for the three months leading up to December 2, 2010.
The confirmation has prompted Dunbar and Monk to call for an independent inquiry into the Pike MIne disaster following the denial of "crucial" evidence.
"We have been seeking information from them for over two years and they have consistently delayed and denied evidence exists," the pair said.
"It is important to note that from the date of the first explosion when police landed at Pike River they took full liability of every action and inaction that happened during the rescue and recovery phase."
After learning about Scada data, electrical expert Richard Healey told Dunbar and Monk the first thing police should have done was look at the data.
"It's beggars belief the Police never looked at Scada beyond the first blast," he said.
"Scada could prove what caused the second explosion, just as it provided strong clues to the cause of the first explosion in the Department of Labour report.
"I just can't believe this. I can't believe they never looked at Scada data in their conveyor belt investigation."