Goldminer Newcrest is disappointed that part of a tailings dam collapsed at its Cadia mine in NSW but is still searching for answers on why the breach happened.
Cadia is one of Australia's largest gold-mining operations, located near Orange in NSW.
Newcrest was forced to halt production at its biggest and lowest-cost mine at the weekend after a breach in the northern tailings dam on March 9 resulted in material flowing into the adjacent southern tailings dam.
Newcrest chief executive Sandeep Biswas says it is less than a week after the breach occurred, so the company is still conducting assessments and is considering how and when it can restart production.
"I do want to say how disappointed I am that this has happened," Mr Biswas said on Thursday.
"We're committed to understanding how it happened and what we can learn from it."
Mr Biswas said that since the breach occurred there has been no widening of the gap in the northern tailings dam, but more material from the northern dam has moved into the southern dam.
Newcrest believes the southern dam has sufficient capacity to manage further movement of material from the northern dam.
"However, further work is being undertaken, and we're engaging international experts to assist us in our view," Mr Biswas said.
The deposit of more tailings into both the northern and southern dams has been halted.
Newcrest is considering options such as diverting tailings into the old Cadia Hill open pit mine which is no longer operational.
The ideal scenario would be to restart depositing tailings into the southern dam and also to get a permit for the old Cadia Hill pit to be used as a tailings storage facility.
If that happens, full production could restart and Newcrest could focus on the repair of the northern dam wall.
"Even without access to tailings storage, we're looking at whether it makes the most sense to recommence mining operations in order to stockpile ore on the surface for future years," Mr Biswas said.
Furthermore pre-feasibility studies on the mine and plant expansion are continuing, still with a completion target of August 2018.
Newcrest says no-one was injured as a result of the breach at the northern tailings dam and has observed no environmental damage.
The company says it does not use mercury, cyanide or arsenic in the production process at Cadia.
Newcrest on Thursday confirmed it will miss its full-year production guidance and will be unable to satisfy contracts for copper concentrate product because of the Cadia mine closure.
The Cadia mine was closed for three months last year because of earthquake damage.
The government's Geoscience Australia Earthquakes site reported a 2.7-magnitude seismic event south-west of Cadia on Thursday, the day before Newcrest says it first noted cracks in the northern tailings dam wall.
Shares in Newcrest were down one cent, or 0.05 per cent, at $19.96 at 1355 AEDT.
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