South African transport utility Transnet is investigating its suppliers for kickback payments to third parties, the company’s chief executive Siyabonga Gama told reporters on Monday.

Allegations of corruption in state firms escalated this year after local media reported on more than 100,000 leaked emails and documents which they say show influence-peddling in the issuing of lucrative tenders, many of which relate to the Gupta family, wealthy businessmen accused of using their friendship with President Jacob Zuma to win state contracts.

 Zuma and the Guptas have denied any wrongdoing.

 “We have gone to each and everyone of our suppliers and we have said to them in terms of the contracts that you received from Transnet are you paying any commission to a third party,” said Gama.

 Transnet said in July it had hired an external legal team to investigate allegations reported widely in the local media that implicated the rail and logistics firm in corruption concerning the purchase of locomotives.

 Europe’s top technology company, SAP put four senior managers in South Africa on leave in July and begun a probe, with results expected this week, into allegations it paid kickbacks to clinch a deal with Transnet and other state-owned firms worth 1 billion rand ($77 million) Gama said they will be receiving some of the reports done by their auditors this week.

 “As soon as the investigations have been completed we will be able to share,” said Gama.

 Regulators in the United States and Britain said last week they were looking into links between South Africa’s Gupta family, the country’s government and banks they may have used to move money amid an escalating graft probe.

 The probe would include both current and past staff at Transnet.

 Transnet operates nearly three-quarters of the African rail network, the bulk of which is in South Africa, but it has been looking to expand abroad.