Hillary Clinton says campaign unaffected by email scandal

Democratic presidential candidate Hillary Clinton speaks during a campaign event at Uncle Nancy's Coffee in Newton, Iowa, September 6, 2015. [Photo/Agencies]

The State Department has confirmed that," she said.

As in her interview with MSNBC on Friday, Clinton said she had never exchanged any information marked classified via the private email system but also acknowledged that it would have been a "better choice" if she had use two separate email accounts.

At a press conference in March, Clinton said she had exchanged about 60,000 emails from her private email account during her stint in the Obama administration, among which about half were personal and thus deleted. The Clinton camp turned over the other half, 30,000 emails in total, to the State Department last year.

The controversy around Clinton's emailing practice burst into public view earlier August after the inspector general for the US intelligence community revealed that two of the thousands of emails held by Clinton contained top-secret information.

"There is always a debate among different agencies about what something should be retroactively (marked classified)," Clinton said on Monday. "But at the time, there were none. So I'm going to keep answering the questions and providing the facts so that people can understand better what happened."

Also, Clinton's Republican rivals have long claimed that Clinton had deleted certain work-related emails, mainly on the 2012 Benghazi attacks that claimed four American lives, including the US ambassador to Libya, to protect herself.

Clinton will attend a congressional hearing in October on the 2012 Benghazi attacks, and the email controversy is likely to assume a predominant role in the hearing.