Greymouth (New Zealand), Dec 12(ANI): The ventilation shaft at New Zealand's Pike River Coal mine has finally been capped, police have said.
According to the New Zealand Herald, a helicopter operation on Sunday saw two 770kg semi-circular steel plates fitted into place over the ventilation shaft, and secured with sandbags.
It has been over three weeks since the first explosion at the mine in Greymouth, which left 29 miners dead.
It was hoped that the cap would help trap the carbon dioxide being emitted by the Gorniczy Agregat Gasniczy (GAG) engine at the mine's entrance, to control oxygen levels and prevent more fires.
Police Superintendent Dave Cliff said that gas levels would be closely monitored for several hours after the capping.
If results indicated a stable environment, the GAG engine will be shut down temporarily for maintenance, and more concrete will be added to the sealing of the portal.
"From that point it will be a case of maintaining a stable atmosphere inside the mine," Cliff said.
If oxygen levels stay low with the cap in place, the GAG engine may not need to run continuously. (ANI)