The Pike River recovery team has been given the green light to go further into the mine's drift.
Worksafe on Wednesday morning confirmed they'd accepted the plan to re-enter the mine beyond the 170 metre barrier.
The team has previously gone 170m in - but the latest announcement will allow them to go beyond that for the first time.
"We have always known the recovery process could be done safely and now we have confirmation of that from WorkSafe," said Pike Family Reference Group spokesperson Sonya Rockhouse.
Family members say many thought it was never going to happen.
"We're looking forward to the agency breaching the 170m seal, recovering the drift and the evidence within it," Rockhouse said.
The next phase will see a push through the remainder of the 2.3km drift, with forensic examinations happening along the way.
It will be welcome Christmas news for the families of the 29 miners who died in the 2010 disaster, the Government says.
"We need to find out as much as possible about what caused 29 men to go to work and not come home," Minister responsible for Pike River re-entry Andrew Little said.
"Now the agency will proceed with what it considers to be the best and safest way to ventilate the drift."
In October, thirty family members took the opportunity to visit the 170m seal drift.
The family members went the furthest they'd ever been allowed into the mine.