Ambassador Caroline Kennedy and senior staff at the U.S. embassy in Japan used personal email accounts for official business, an internal watchdog report said Tuesday -- making Kennedy the latest Obama administration official to run afoul of email security guidelines.

The State Department’s Office of Inspector General (OIG) report said it received reports concerning the use of private email accounts for official business, and identified instances where emails labeled "sensitive but unclassified" were sent from or received by personal email accounts. 

“On the basis of these reports, OIG’s Office of Evaluations and Special Projects conducted a review and confirmed that senior embassy staff, including the Ambassador, used personal email accounts to send and receive messages containing official business. In addition, OIG identified instances where emails labeled Sensitive but Unclassified were sent from, or received by, personal email accounts," the report said.

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The OIG stressed that department policy says employees generally should not use private accounts for official business, citing the risk of hacking and data loss. 

"Employees are also expected to use approved, secure methods to transmit sensitive but unclassified information when available and practical," the report says.

The report, conducted between January and March, comes as the same OIG office reviews email use and policies across the department amid the controversy over former Secretary of State Hillary Clinton's use of a personal email and server. The FBI is reviewing the security of that server, with questions mounting over whether classified material was improperly shared or stored on the Clintons' private account. 

Email issues aren't confined to the State Department. The IRS admitted Monday to a federal court there was a second personal email account -- set up under the name "Toby Miles" -- that Lois Lerner, the official at the heart of the Tea Party targeting scandal, used to conduct agency business.

But State Department messages can cover a range of sensitive and classified material involving America's allies and enemies. The OIG report does not appear to suggest a serious information breach. Sensitive but unclassified information can be shared outside of the government, though officials are required to use discretion. However, it puts further spotlight on the department's struggle to keep its information secure.

Kennedy, daughter of President John F. Kennedy, has been ambassador to Japan since November 2013.

The report also noted the economic section of the embassy – which works closely with the United States Trade Representative on the Trans-Pacific Partnership – was not maintaining centralized files, and the embassy has not enforced department or federal regulations on managing records.

“Officers have individual files based on their own filing systems, located in personal folders on a shared drive and in Microsoft Outlook email personal folders. These files are not accessible to anyone else and are not archived, retired, or retrievable,” the report said.

Asked about the report, a State Department official told The Associated Press that the embassy in Japan requires the use of official email accounts to conduct official business whenever possible, and indicated that Kennedy and other staff are acting on the inspector's recommendations.

"Ambassador Kennedy uses an official email address for official business. As the report reflects, in the past, like others at the mission, Ambassador Kennedy infrequently used her personal email account for official business," said the department official, who was not authorized to speak on the record and requested anonymity.

"This is allowed, so long as measures are taken to ensure that official records sent or received on personal email are preserved and other requirements are observed. The ambassador and embassy staff are implementing the OIG recommendations, including those regarding emails," the official said.

The Associated Press contributed to this report.