PERTH (miningweekly.com) – The share price of ASX-listed Aditya Birla fell by 20% on Wednesday over uncertainty about the restart of the Nifty copper operation, in Western Australia, where a sinkhole was discovered.

The Department of Mines and Petroleum (DMP) in March issued Aditya Birla with a notice prohibiting all mining operations at Nifty.

The company provided a risk assessment to the DMP, and was subsequently allowed to start a phased investigation into the sinkhole. The first stage of the investigation was scheduled for completion at the end of May, at which time the company would move forward with the investigation, subject to DMP approval.

All further activities at Nifty would be dependent on the completion of the phased investigation, Aditya Birla said.

Furthermore, dewatering of the openpit has progressed ahead of schedule, and work on diverting the underground water flow away from the openpit was currently in progress.

Aditya Birla had also appointed external consultants to review the current mining plan at Nifty.

The suspension of operations has resulted in the majority of employees at the Nifty mine being stood down, and the company said that it remained in communication with all employees, adding that a conference has been called for the end of April to consider employee concerns.

Meanwhile, the miner also reported on Wednesday that copper production for the three months to March had declined by 21% on the previous quarter, reflecting the fact that its Mt Gordon operation, in Queensland, was placed on care and maintenance in April last year.

Some 9 186 t of copper was produced during the quarter under review, compared with the 17 093 t produced in the previous corresponding period. Production during the quarter was sourced solely from the Nifty operation.

The copper miner on Wednesday said that it would not provide a full-year production guidance, as it could not estimate with any certainty when mining operations at Nifty would resume.

Aditya Birla’s shares were trading at a low of 15c a share on Wednesday, down from the previous day’s closing price of 29c a share. The stock closed at 23c a share in the afternoon.