Britain’s anti-fraud regulator has opened an investigation into suspected corruption in Australian-British miner Rio Tinto Plc’s business conduct in the Republic of Guinea, the agency said.

In a statement on Monday, the Serious Fraud announced the probe into the company, one of the world’s largest metals and mining corporations, its employees and others associated with it.

In November Rio Tinto said it had become aware of emails that referred to unexplained payments of $10.5 million in connection with the Simandou iron ore project in the West African nation.

“Rio Tinto will fully co-operate with the Serious Fraud Office and any other relevant authorities, as it has done since it self-reported in November 2016,” the company said in a statement on Monday.

Guinea’s Mines Minister Abdoulaye Magassouba said by telephone that he “would not comment on a judicial matter, especially at this stage.”

“We are continuing the work of developing the Simandou project,” he added.

U.S.-listed shares in Rio Tinto were unchanged at $43.90 in after-hours trading after closing 0.5 percent lower.

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Reporting by Huw Jones; Additional reporting by Saliou Samb in Conakry; editing by Alexander Smith and Richard Chang