Hillary Clinton failed to turn over an email to the State Department in which she appears to stress the importance of keeping the correspondence on her private server away from prying eyes, the Associated Press reported on Friday.
In an exchange from November 2010, Clinton's closest aide, Huma Abedin, asked Clinton if she wanted to set up a state.gov email address to get around the State Department's spam filter, which was blocking messages from her personal account.
Clinton responded, "Let's get separate address or device but I don't want any risk of the personal being accessible."
A copy of the exchange was included in a report by the State Department's inspector general from last month, but was not part of the batch of 55,000 messages that Clinton was ordered to hand over. Abedin, who also used a private account on Clinton's server, provided the message to the State Department after she was asked to surrender her own work-related emails, according to the AP.
"Secretary Clinton had some emails with Huma that Huma did not have, and Huma had some emails with Secretary Clinton that Secretary Clinton did not have," Clinton spokesperson Brian Fallon told the AP.
Related: FBI reveals 'additional details' about Clinton email probe in secret declaration
Fallon maintained that Clinton turned over "all potentially work-related emails" after the State Department's initial request in 2014, but he declined to say why the 2010 exchange with Abedin was not included.
Clinton was allowed to withhold non work-related emails, such as messages that discussed planning for her daughter's wedding, but Friday's revelation suggests there may have been some pertinent missives that she knowingly refused to give up.
The computer technician who set up Clinton's private email server refused to answer questions more than 125 times in court this week, according to transcripts of the deposition that were released on Thursday. The employee, Bryan Pagliano, cited his Fifth Amendment privileges when asked what role he had in setting up the server, who paid for it, and what other State Department employees knew about it or used it.
Clinton has apologized for using a private email server for official business while she led the State Department from 2009 to 2013. Thousands of Clinton's emails have been released in response to a FOIA lawsuit filed by VICE News.
While Clinton insists she did nothing wrong, the FBI continues to investigate her use of a private email server, and the controversy has hung over her campaign for the Democratic presidential nomination for months.
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