Pike River Coal chairman John Dow says safety is a cornerstone of everything the company does, and while people have raised some concerns, they also recognise that a Royal Commission will find out what caused the blasts.
Twenty-nine workers died in company's mine near Greymouth in a series of explosions that began on 19 November.
A former worker at the mine, Brent Forrester, told TVNZ's Sunday programme that he and some of his colleagues have had concerns about safety since last year. Mr Forrester worked at Pike River Coal mine from August 2008 until July 2009.
He said he and several colleagues were worried about the levels of methane gas in the mine and, at times, there were problems with some of the methane censors not calibrating.
Mr Dow told Morning Report he understands Mr Forrester's situation as he grieves for colleagues. He says a number of concerns have been expressed anecdotally but no-one had felt sufficiently concerned to raise the issue with management.
Mr Dow says the company isn't retreating into any corner. "We've said right from the beginning that we wanted to get to the bottom of this, that we would be holding our own inquiry."
Engineering, Printing and Manufacturing Union national secretary Andrew Little says Mr Forrester's comments are credible and consistent with what he has heard.
Mr Little says it is natural that a lot of talk starts happening but no-one quite knows what can be verified.
He says from what he has heard from his members there is a culture of having concerns but being fearful about raising them.
When asked whether staff were encouraged to discuss safety issues, Mr Dow said they were and that safety was the cornerstone of everything the company does.
The Government last week agreed to establish a Royal Commission into the tragedy, while police, the coroner and the Department of Labour will also conduct inquiries.
The company has revealed it will appoint a top international investigator to carry out its investigation.