The receivers for Pike River Coal Ltd say the process of selling the mine is taking longer than originally anticipated.
The company went into receivership in December, a month after the West Coast mine was closed following the deaths of 29 workers.
Earlier this year, John Fisk of PricewaterhouseCoopers said he expected the sale of the mine would be finalised by August.
The original timetable has now been extended to allow for further due diligence to be done by a number of short-listed parties.
Mr Fisk says several site visits by bidders will take place in the next few weeks, and it is hoped final bids will be received by the end of September.
He says it is difficult to know when the sales process could be completed as consents will be required from various government agencies.