Judge Jane Farish yesterday released her 64-page judgment to explain why she blamed the company for causing the explosion and subsequent deaths of the men.

Farish convicted Pike River Coal Ltd last month on nine health and safety charges laid by the former Department of Labour.

The Greymouth judge said the breaches were "causative of the explosion and the subsequent deaths of the men who perished".

In her reserved judgment, she said the company failed to implement its own inadequate safety plans and procedures, resulting in an unsafe environment developing and worsening over a number of years.

In the decision, the judge said the company "should have ceased mining to allow for the risk of unpredictable but foreseeable events", according to Radio New Zealand.

Farish found the company failed to take a number of steps to manage methane gas underdground, including the management of diesel emissions from vehicles, the drainage of gas from the coal seam and allowing numerous potential ignition sources in the mine's restricted zone.

Its electrics and gas sensors had not been checked for four months before the explosion and only one of three methane sensors in the danger area was operational, according to New Zealand News.

The judge said the geology of the land had not been properly investigated and the fresh air base, used as an emergency retreat zone, was inadequate and required a miner to climb a series of vertical ladders over 100 metres, or to evacuate through the main 2.3km tunnel.

Farish will sentence the company in the Greymouth District Court on July 4-5.

Each of the nine charges carries a maximum penalty of $250,000.

A trial date for chief executive Peter Whittall has yet to be set, but to date he has denied all 12 charges laid against him under the Health and Safety in Employment Act.