Caroline Kennedy, the United States ambassador to Japan, and several other senior American diplomats there have used personal email accounts to conduct State Department business, the inspector general for the department said in a report released Tuesday.

The inspector general, Steve A. Linick, identified instances in which “sensitive but unclassified” information was sent and received on personal email accounts, the report said.

The criticism of Ms. Kennedy and the other diplomats came as Hillary Rodham Clinton, who is seeking the Democratic nomination for president, has faced questions about her exclusive use of a personal email account when she was secretary of state. That account was run through a private server that Mrs. Clinton kept at her New York home.

The report on the embassy in Japan said the inspector general’s office “has previously reported on the risks associated with using commercial email for official government business.” It added that “such risks include data loss, hacking, phishing and spoofing of email accounts, as well as inadequate protections for personally identifiable information.”