The preliminary hearing will iron out who must attend the inquiry hearings and the witnesses or submitters who are likely to have valuable evidence.

This hearing will also set the procedures the inquiry intends to adopt.

“The suggested procedures are based on the fact that the commission is conducting an inquiry,” the commission said.

“It is not conducting a trial of anyone. Nor is it investigating whether anyone might face prosecution for breach of the law – that is a matter for the Police and the Department of Labour.”

There will be four broad phases of subsequent hearings, with the first phase to put the mining tragedy “in context” over two weeks starting May 23.

The next phase, starting July 4, will delve into the search and rescue operations over three weeks.

The third phase is on what happened at the mine and will last eight weeks with the first part from August 8 to September 2 and the second part running from September 12 to October 7.

The final phase will look into policy considerations, lasting two weeks from October 25.

Causes of the disaster

As part of the third phase of the hearings, the commission will seek to identify the primary cause of the explosions.

Considerations include the hazards and flammable gas present in the mine immediately prior to and at the time of the incident, the locations of the men and their activities at this time, the likely ignition source and the cause of the subsequent explosions.

The commission will investigate Pike River Coal’s management and operational practices and the health and safety systems used.

Possible impediments to health and safety systems will also be reviewed, including whether the location and design of the mine created issues and whether financial difficulties or production delays had an impact.

The ventilation and gas monitoring systems in place at the mine, and communications systems from underground to the surface will also be scrutinised.

The methods used by regulatory agencies to provide external oversight of the safety regimes at the mine is another area to be covered in the third phase of hearings.

There are at least 38 witnesses or submitters of evidence lined up so far.

Aside from Pike River Coal, government departments and agencies, and the unions, there will be representation from the Pike River Contractors and Suppliers Group, Coal Services, Valley Longwall International, Solid Energy, New Zealand Oil and Gas, McConnell Dowell Constructors and the Mines Rescue Trust.