The FBI has been looking at individuals, bank accounts and companies in the US that could be linked to South Africa’s Gupta family.
The FBI has opened an investigation into US links to South Africa's Guptas, escalating a scandal over the family's alleged use of a friendship with President Jacob Zuma to control state businesses, the Financial Times said on Thursday.
Separately, Britain's banking regulator, the Financial Conduct Authority (FCA), said it was in contact with two UK banks over any possible links to the Gupta family.
The Guptas and Zuma have denied any wrongdoing. Gupta family spokesman Gary Naidoo could not be reached for comment and the US Embassy in Pretoria had no immediate comment.
The family, founders of a business empire spanning media, mining and consulting, have been named in a trove of leaked emails alleging graft in dealing with South Africa's state-owned companies, which also named several global firms.
The Financial Times, which cited "people familiar with the matter", said US investigators had been looking at individuals, bank accounts and companies in the US for ties to alleged graft involving the family. It gave no further details.
Britain's FCA said it was in contact with HSBC and Standard Chartered banks following reports in British newspapers that the finance minister had asked regulators to investigate the lenders' possible ties to the Gupta family and Zuma.
"The FCA is already in contact with both banks named and will consider carefully further responses received," the regulator said.
Standard Chartered in London said they were not able to comment on details of client transactions but added that "after an internal investigation, accounts were closed by us by early 2014”. HSBC said it had no comment on the matter.
Britain's parliament is expected to discuss British banks’ possible involvement in the Gupta case on Thursday.
Zweli Mkhize, one of several potential candidates to replace Zuma as head of the African National Congress in December, said the United States and Britain were within their rights to investigate.
"If there is any information suggesting corruption or irregularities, it needs to be investigated across the borders. It should not be restricted to South Africa," he told reporters.
The Guptas and their companies have not been charged with any crime in South Africa, but the scandal is one of many that have dogged the Zuma presidency.
Local media have reported extensively on the so-called "Gupta-leaks" - thousands of emails between the Guptas and their lieutenants and state-owned companies, politically connected individuals and private sector firms.