Pike River Coal has undertaken, via its receiver PricewaterhouseCoopers, to submit a proposed recovery plan, but a decision will not be made until the new year, New Zealand Energy Minister Gerry Brownlee told Newstalk ZB.

“The initial expectation was the GAG machine would make the mine inert and begin to get it into a position where it could be entered in a matter of hours. It's now been 21 days and we're nowhere near that point,” he said.

Brownlee has sought to reassure the families that all options are being explored after it became clear the current plan was taking too long.

He said independent expert advice would be sought on whether the new plan was workable. It would need to be reviewed by the government which could take several weeks.

The key issue in deciding whether a recovery could take place was the safety and stability of the mine, not cost, he said.

Meanwhile, the inertisation process using the GAG and the Floxal nitrogen generator, which arrived onsite over the weekend, is continuing.

The Floxal has been operating all night at Pike River in tandem with the GAG to neutralise and cool the environment within the mine, NZ Police said in a statement.

The GAG will be turned off at some stage to measure the effect the Floxal is having on the environment.

The situation is being monitored with real-time gas testing. Overnight those readings were described by NZ Police as "positive".