Pike River Coal's largest creditor says the mine sale process could continue until next year.
Pike River Coal Ltd went into receivership in December last year, after the mine was closed after 29 men died in a series of explosions at the West Cost mine on 19 November. Their remains are still in the mine.
The mine's biggest shareholder, New Zealand Oil and Gas, is owed at least $66 million.
Chief executive David Salisbury says he is encouraged by the number of bidders, some of which are foreign entities.
Mr Salisbury says final bids for the mine are due before the end of the year, but completing a sale could take longer due to the sensitivities involved and possible regulatory issues if the mine is sold to a foreign company.
NZOG posts $75.9m loss
New Zealand Oil & Gas has posted a full-year loss of almost $76 million due to a significant write-down in its investment in Pike River Coal Ltd.
The company lost $75.9 million in the year to June, compared with a $3.9 million loss the previous year.
The result includes a $99 million write-down of its investment in Pike River Coal.
Normalised profit was $30.6 million, more than double the $14.7 million reported a year earlier.
Oil & Gas chief executive, David Salisbury, says it was a very successful year for its operations, with revenue rising 7% to $106.5 million.
He says the Kupe field had strong earnings, largely in line with expectations, with just over $66 million in revenue and Kupe has now replaced Tui as the company's major income earner.