Glencore, the world’s biggest mining company, is under investigation by US authorities for alleged money laundering.
Shares in the Anglo-Swiss firm fell more than 11% in London, wiping more than £5bn off its market value, after it revealed it had been ordered to hand over documents to the US Department of Justice.
The subpoena relates to compliance with the Foreign Corrupt Practices Act and US money laundering laws, Glencore said.
The investigation is centred on business dealings in Nigeria, the Democratic Republic of Congo and Venezuela, and date from 2007 to present.
“Glencore is reviewing the subpoena and will provide further information in due course as appropriate,” the company said in a brief statement.
The company has copper and cobalt operations in Congo, and trades with Nigeria and Venezuela. It accounts for more than a quarter of the world’s cobalt output, most of it from Congo.
The Paradise Papers revealed last year that Glencore secretly loaned tens of millions of dollars to an Israeli billionaire, Dan Gertler, after it enlisted him to secure a controversial mining agreement in the Democratic Republic of the Congo.
US sanctions on Gertler, Glencore’s former Israeli partner, triggered litigation in Congo that threatened to disrupt supplies of cobalt from the world’s biggest producer of the metal.
Glencore recently settled a mining dispute with two companies associated with Gertler by agreeing to pay royalties. It also reached a settlement in another dispute involving its Kamoto copper and cobalt mine in the country, but remains at odds with the Congolese government over a new mining code.
Glencore and Gertler have consistently denied any wrongdoing in their business deals.