The team recovering the Pike River mine has reached the area that provides the best chance of finding clues about what caused the 2010 explosion.
Known as Pit Bottom in Stone, the network of 600m of tunnels - off both sides of the entry tunnel - contains electrical equipment and the loader driven by one worker to escape alive.
A six-person team including Pike River Recovery Agency chief operating officer, Dinghy Pattinson, reached the area early this afternoon.
Pattinson said the tunnels would not be forensically examined for a number of weeks.
In the meantime, a team will continue to recover the last 350m of the entry tunnel before a seal that separates the tunnel from the main workings of the mine.
Pike River families have welcomed the recovery milestone.
Pike River widow Anna Osborne, who is also the Family Reference Group's chair, said the recovery of Pit Bottom in Stone needed strong scrutiny.
"The families need to know that the scene examination will be done by the best experts, using the right equipment and knowledge.
"This is an absolutely critical part of the recovery and we are being very clear with police and the recovery agency that it must be a focused effort and that there needs to be transparency to ensure families can trust the outcome."
Sonya Rockhouse, who lost her son Ben in the explosion, said reaching Pit Bottom in Stone had been an important goal for years.
"This is the one place likely to hold evidence crucial to seeing justice being done.
"There are a lot of conspiracy theories floating around about Pike that have caused a lot of grief to family members. This is the chance to get a clear run at the truth."
Rowdy Durbridge, who worked at Pike River and whose son Dan died in the explosion, said justice was coming closer.
"It's been a long and difficult journey this far, but it's feeling closer and closer to the end. If you'd asked me six years ago when we'd all given up hope that we'd get to this point I'd have wept. Now we are here."