Newly released emails are alleged to show links between the US state department and the Clinton Foundation Foundation during Hillary Clinton's time as secretary of state.
The latest batch of documents has been released by the Judicial Watch conservative watchdog group, and includes 296 pages of records.
The website, which obtained the documents as part of a freedom of information lawsuit, says the release includes 44 email exchanges that Mrs Clinton did not hand over to the state department.
Many of the documents are censored or redacted, with details such as names blocked out.
Some of the emails involve communication between the state department - which was headed by Hillary Clinton between 2009 and 2013 - and the Clinton Foundation, the non-profit organisation founded by Bill Clinton.
One email exchange appears to show former Clinton Foundation official Doug Band lobbying Hillary Clinton aides at the department for a job for an associate.
Mr Band writes that it is "important to take care of [redacted]".
He is informed that "we have all had him on our radar. Personnel has been sending him options".
In another exchange, the two aides are encouraged by Mr Band to put Gilbert Chagoury - a Lebanese-Nigerian billionaire and key Clinton Foundation donor - in touch with the state department’s 'substance person' on Lebanon.
Judicial Watch, claims that "Clinton’s top aides’ favors for and interactions with the Clinton Foundation seem in violation of the ethics agreements that Hillary Clinton agreed to in order to be appointed and confirmed as Secretary of State".
In a statement published by CNN, Josh Schwerin, spokesperson for the Clinton campaign, said: "Neither of these emails involve the secretary or relate to the Foundation's work.
"They are communications between her aides and the President's personal aide, and indeed the recommendation was for one of the Secretary's former staffers who was not employed by the Foundation," he added.
Emails related to Mrs Clinton's time at the state department have proven a major source of controversy for the Democratic presidential candidate.
Her use of a private email server has been heavily criticised by opponents, in particular her Republican rival Donald Trump.
Mrs Clinton has repeatedly said that no email she sent or received was marked classified.
After an investigation, FBI director James Comey concluded that "no charges are appropriate" despite "extremely careless" behaviour by Mrs Clinton and her staff.
The US state department last month restarted its own internal investigation into the use of the private email server.
