Mount Gibson Iron has cut its sales guidance and warned that repair works at its Koolan Island mine might take three months and cost up to $10 million.
Mining in the main pit at the iron ore mine, in Western Australia's Kimberley region, was suspended a fortnight ago due to damage to its main pit.
Further minor instability occurred on the weekend during repair works, the company said.
Mount Gibson has lowered full year sales guidance to 6.0 to 6.4 million tonnes for the 2015 financial year, from 6.6 to 7.0 million tonnes.
An assessment found that additional repairs were needed to enable production to be safely resumed, the company said.
The planned remediation work might take about three months to complete, with an estimated capital cost of $5-10 million, it said.
Mt Gibson shares have been hammered in 2014, falling from a year high $1.20 in February to 44 cents at the start of trade on Monday as the iron ore price has dived.