US regulators have questioned large US banks, including Morgan Stanley and Citigroup, about their international hiring practices as they press ahead with their investigation into foreign banks in China.

The Securities and Exchange Commission has sent letters to the Wall Street banks to ask about their China businesses following the launch of a probe into JPMorgan. People with knowledge of the requests said they did not amount to a formal investigation and that multiple banks had been contacted with similar questions in the wake of the JPMorgan allegations. The SEC declined to comment.

JPMorgan disclosed in August that it was turning over information to the SEC and the Department of Justice as part of a probe into whether it hired family members of influential figures in the Chinese government and elsewhere in Asia in an effort to win business.