The fourth explosion struck at 1:42pm yesterday with Pike noting it appeared that the subsequent fire involved coal as well as gas.

This most recent explosion was said to be stronger than the second explosion on Wednesday, which ended hopes of survival for the 29 miners.

Underground footage already suggested the second explosion was more powerful than the first explosion more than a week ago, while the third explosion on Friday was relatively minor.

The Queensland Mines Rescue Service has continued preparations to deploy its GAG inertisation unit at the mine over the weekend.

The GAG unit is basically a jet engine that will overwhelm any fires and explosive gases underground with nitrogen, carbon dioxide and water vapour.

In a management update released yesterday, Pike said it would be deployed either overnight or this morning.

QMRS state manager Wayne Hartley previously told ILN it could take 4-6 hours to inert the mine, but it might need to be inerted twice.

Rescuers will be able to enter the mine to start the recovery operation once the underground environment is completely managed.

Management update

Pike is facing a series of inquiries over the mining disaster.

While it cooperates with separate inquiries from the coroner and the Department of Labour, the company expects the New Zealand government to release the terms of reference for its Commission of Inquiry this week.

The company will also continue its own internal investigations.

"We are as determined as anyone else involved to find the reason or reasons for what has happened," Pike chairman John Dow said.

“If this internal inquiry turns up, any information which would be of assistance to any of the other inquiries, we would of course make that known to police investigators."

While the focus remains on recovering the bodies of the lost miners for their families, the board delved into the possibility of reopening the mine, which would need a commercial feasibility assessment.

“It is imperative that the company be able to assess the level of damage to the mine as soon as possible in order to reach meaningful conclusions about the options available to us," Dow said.

"Once we can get back underground, Pike will be an advanced development project, given that all surface infrastructure remains intact, including surface facilities, pipelines, the coal preparation plant, roading and rail load-out facilities at Ikamatua."

Once the damage is assessed, Pike can also lodge an insurance claim with its material damage and business interruption coverage totalling $NZ100 million.

Major Pike stakeholder New Zealand Oil and Gas, along with Bank of New Zealand, both recently provided a 90-day standstill period over Pike’s debt due from its $25 million working capital loan facility.

Pike also received the remaining $12 million of this facility on Friday.

Dow was thankful for the “breathing space” provided.

"The further funding and the coal that the company has available for sale provide us with the basis to support our employees at this time and best assess our financial needs."

While Pike has issued force majeure notices to parties in its coal transport arrangements, the company added it would be discussing its commercial relationships with other contractors and service providers.

Supporting the Pike River families

"There has been an incredible outpouring of support in the last week for the families affected by this tragedy and also for the business itself,” Dow said.

“Peter Whittall [Pike chief executive] and I are personally moved by all of this. It is heartening to see the level of public support for the funds that have been established for the families and the wider community."

Donations to the company’s tax-deductible Pike Miners Relief Fund can be made by:

• Direct credit to: Minter Ellison Rudd Watts Trust Account – for Pike River Miner’s Relief Fund

  National Bank of New Zealand, Featherston Street, Wellington, New Zealand

  Account Number: 06-0501-0121759-02

• or by post to: Pike Miners Relief Fund, PO Box 2793, Wellington