Tomorrow's planned re-entry to Pike River Mine drift delayed

Tomorrow's planned re-entry of the Pike River Mine drift will not go ahead.

A three-man search team was due to enter the drift tomorrow, however a safety issue means work to re-open the site has been halted and entry will have to be delayed.

Twenty-nine men died in November 2010 after two methane blasts tore through the mine.

"We've had a bit of a set back," Minister Responsible for Pike River Re-entry Andrew Little said today.

"Unexpected and unexplained readings were reported by the atmospheric monitoring systems in the Pike River mine."

Mr Little described it as a "temporary set back" and that it shows unpredictable elements of the drift.

"You go on the expert advice... they're all saying they could not expect this."

He could not predict when the mine would be re entered.

"It's the mix of methane and oxygen that increases the risk."

He said there was a variable read at the end of the drift that could not be explained. It was detected yesterday and confirmed overnight. 

"Obviously it's disappointing but we are going to observe safety first," Mr Little said. 

"The Prime Minister and I will join the families on the West Coast tonight and the families will receive a comprehensive briefing from the Agency tomorrow," Mr Little said. 

"The families insisted safety must come first.

"No more lives must be put at risk," he said.

The late development will be a big blow for victims' families, who have battled for the site to be re-opened in a bid to find out how the accident happened.