Harmony Gold, the previous mine owner, said the incident was a criminal matter, which it handed over to police for further investigation.

Company plans to undertake 4,015 metres of reverse circulation drilling across 11 holes this year, targeting resource expansion and exploring new prospects.

Further rate increases are “a pretty good guess” of where the central bank is heading, Powell said on Wednesday.

Washington last month included Polyus and Polymetal's Russian business on its list of sanctions targets.

Total resources in the indicated category are estimated at 57.1 million tonnes grading 1.11 g/t gold, for approximately 2 million gold ounces.

Expansion will increase and modernise Kalgoorlie Consolidated Gold Mines processing capacity from 13 million tonnes per annum to 27 mtpa.

Switzerland is the world's biggest bullion refining and transit hub.