LONDON (AP) — U.K. authorities are investigating allegations that British banks inadvertently acted as conduits for money laundering linked to corruption in South Africa.

British Treasury chief Philip Hammond passed on allegations raised in a letter by former Cabinet Minister Peter Hain to the Financial Conduct Authority, the National Crime Agency and the Serious Fraud Office.

Hain raised concerns in a letter to Hammond that banks, including HSBC and Standard Chartered, may have been linked to laundered money.

The allegations center on South Africa's President Jacob Zuma and a wealthy business family, the Guptas.

HSBC declined to comment.

Standard Chartered declined to comment on client transactions, but confirmed that "after an internal investigation, accounts were closed by us by early 2014." Standard Chartered says it takes combating financial crime "very seriously."