Family of the miners who died in the Pike River disaster say the government have misled them over plans to seal the mine.
Sonya Rockhouse, whose son Ben died in the mine, said the details of the planned seal "show once again they have been lied to".
"The next stage is to fill the mine-shaft completely from floor to ceiling with concrete... it will be permanent."
"Rather than send Ministers to threaten us with arrest, John Key should be calling a halt to the sealing process and talking to us about re-entry."
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Family members of the men who died in the November 2010 disaster had blocked the mine's main road this week.
"Promises were made by the Prime Minister and they haven't been kept. Anyone who loses family like this deserves justice and closure."
The families of the Pike River victims met with Environment Minister Nick Smith in Greymouth to discuss closing the mine.
"I have confirmed to the families that Solid Energy has completed the first phase of work for the permanent seal 30m into the drift," Smith said in a statement.
"I remain doubtful of claims that the mine can be safely re-entered. The mine is full of methane and is likely to have residual heat sources capable of triggering an explosion if there was a source of oxygen. There is the added risk of rock falls.
"Pike River Mine has only one exit route and that remains a fundamental flaw for the safety of any re-entry. The government has spent more than $5 million trying to find a safe way of re-entering the mine and we support the conclusion that it is not practically possible," Smith said.
"I do appreciate the huge loss families have faced with the loss of loved ones at Pike, and the added pain of not being able to recover their men. However, you cannot justify putting further lives at risk."