The Government's decision to stop the Pike River Coal mine recovery operation could mean the loss of vital evidence, the lawyer representing the families of the 29 men killed says.

Police announced on Thursday they were ending their operation and handing the West Coast mine over to the receivers with the remains of the men, who died in a series of explosions in the mine since November 19, still inside.

The families of the men released a statement on Saturday saying the mine was stable and the decision was "flawed and must be revisited".

Receivers have until 5pm today to make a decision about the mine's future - which could include sealing it - and report to police on what they intend to do.

The families' lawyer, Nicholas Davidson, QC, said if the mine was sealed it would stop people entering it to gather evidence for the Royal Commission of Inquiry.

"We're concerned, of course, because one would expect the forensic (information) that could be gained by getting into the mine will be affected in some way, perhaps significantly, by not having that evidence available," he told Radio New Zealand.

The Government had not revealed a "key plank" of its decision to stop the operation, he said.

"We have made no progress at all, since Friday, in unravelling what we see as the mystery of this decision," he said.

The decision seemed to be based on the "alleged failure" of the jet-engined GAG machine, used to blow water into the mine to stabilise the atmosphere, he said.

"(However), we now believe that the atmosphere is stable and so a key part of the decision made to date seems to be, as it were, wrong," he said.

Mine safety expert David Cliff, of the University of Queensland, earlier told The Press that while there was a dramatic improvement in the mine's atmosphere it did not mean it was safe to re-enter. Dr Cliff was among the experts consulted by police before Thursday's announcement the mine would be sealed.

"The atmosphere is now inert without the use of the GAG.

"It's not capable of supporting combustion. It's full of methane, as far as we can detect.

"But then to say everything is OK, we can go enter the mine, that's another quantum leap beyond that," Dr Cliff said.

The GAG machine will leave New Zealand at the end of the month, with Prime Minister John Key last week saying it was burned out.

Meanwhile, contractors unlikely to receive wages owed them by the Pike River Coal company are disappointed about the response to their plight from local charitable trust Development West Coast (DWC).

DWC was established in 2001 to administer $92 million from the government to help promote economic development in the region after native forest logging came to an end.

Today DWC it said it could not directly distribute funds to individuals or businesses despite the hardship facing families, and instead has to consider the implications of the disaster for the region's economy.

About 80 West Coast contractors and suppliers are owed more than $8m dating back to October, but as unsecured creditors the group representing them has been told the only way to recover any money is to apply to the courts to wind up the company.

- NZPA