Prime Minister John Key says he has been assured by Pike River Coal that it had no warning of an explosion at its West Coast mine on Friday.
Mr Key says everyone is still focused on finding the 29 trapped miners, and the time for questions is later.
But he has rejected the suggestion that Australian mines are safer than those in New Zealand. It was wrong to say Australian mines have oxygen tanks - mines in both countries have water supplies, but not food supplies.
Mr Key says he also asked Pike River Coal if there were any warnings of a methane build-up. He was told there was continual monitoring of air quality, there were methane alarms in the mine and each miner carried a gauge. None of these indicated anything was wrong.
Mr Key says questions will have to be asked about what caused the explosion and it is most likely that a commission of inquiry will be set up.