US Ambassador to Japan Caroline Kennedy attends a ceremony at the Peace Memorial Park in Hiroshima, western Japan, August 6, 2015. [Photo/Agencies]

WASHINGTON - US Ambassador to Japan Caroline Kennedy used her personal email for official business despite a State Department policy advising employees generally to avoid this, an internal audit released on Tuesday said.

The State Department's Office of Inspector General made the finding in a routine report on the Tokyo embassy as the agency is under scrutiny for Hillary Clinton's use of a private email address and server when she was secretary of state.

"Senior embassy staff, including the ambassador, used personal email accounts to send and receive messages containing official business," the report said, saying it found "instances when emails labeled 'sensitive but unclassified'" were sent and received on private email addresses.

It did not say whether Kennedy, daughter of former President John F. Kennedy, had sent or received such information.

The report cited risks to using personal email accounts, including data loss, hacking, phishing, and spoofing of email accounts, as well as inadequate protections for personally identifiable information.

State Department spokesman John Kirby stressed that using personal email was not barred by the agency's rules. But he said it was discouraged and that employees needed to ensure that emails were eventually preserved within the US government system.