New Zealand Police immediately ordered the evacuation of the crews when the higher gas levels were registered, forcing a stop to the repair and maintenance of the GAG unit, which is pumping water vapour into the mine.

During the shutdown period gas readings at the mine prompted the evacuation of five contractors who were working near the portal shotcreteing cracks in the seal.

Maintenance on the GAG unit, which arrived from Australia two weeks ago, stopped for about three hours, increasing the danger of feeding underground fires, NZ police said.

Superintendent Gary Knowles said the situation underground was still very unstable.

“Until the GAG can be repaired and reinstated, the situation at the mine is very unstable,” he said in a statement on Monday afternoon.

“This highlights the level of risk being faced by the teams working to stabilise the mine.

“Police will not endanger any lives in what is clearly a volatile situation.”

The GAG at Pike River coal mine was re-started later on Monday but it will take several hours to re-pressurise the mine.

Meanwhile, the NZ government has launched an official website for the Royal Commission inquiry into the Pike River tragedy.

The inquiry will investigate what triggered the methane gas explosion, the subsequent deaths of the men as well as the rescue operations and safety regulations.

The inquiry, which is being lead by Justice Graham Panckhurst, a Christchurch-based High Court judge, also has Queensland Commissioner for Mine Safety and Health Stewart Bell and former Electoral Commission chief executive David Henry as its two other two commissioners.

Justice Panckhurst will be expected to report on the inquiry no later than March 31, 2012.

“We are most conscious of the significant and keen public interest in the Pike River mine tragedy,” Panckhurst said.

“The website will provide an important public face for our work.”