Angry families of the 29 Pike River workers killed in the November 2010 explosion are demanding to know why there has been another set back to the re-entry of the mine.
Bernie Monk. Photo: RNZ
In September last year the West Coast mine's owner Solid Energy and the Government committed to a seven stage plan to enter the main tunnel of the former mine. The work was expected to have been completed by April.
At their fortnightly update with Solid Energy last week, the families were told that an essential methane detector is not certified for use and will take eight weeks to replace.
A spokesperson, Bernie Monk, said on Monday the families have written to the company demanding to know how such a key element could be overlooked.
"I find that most disappointing we find this out because we were all set on re-entering the mine by the end of this month. It's just knocked the wind out of my sails to be honest.
"I want to get to the bottom of how these sort of things happen and make sure that things like this don't happen again for us down the track."
Solid Energy says it is investigating the matter.