Former US Secretary of State Hillary Clinton. Lucas Jackson/Reuters Hillary Clinton "was not that focused" on the private email server she used during her four years as secretary of state and "couldn't control the technical aspects of it," she told "Meet the Press" host Chuck Todd on Sunday.

The presidential candidate has come under fire for using a private account to send and receive work-related emails while she served as secretary of state, which she has apologized for and called a mistake.

Still, Clinton has insisted that what she did was legal, and on Sunday she reiterated that her use of the server was a matter of convenience.

"It was already there," she said of the server. "It had been there for years. It is the system that my husband's personal office used when he got out of the White House. And so it was sitting there in the basement. It was not any trouble at all."

Clinton's unusual email system was originally set up by a staffer during Clinton's 2008 presidential campaign, replacing a server used by her husband, former President Bill Clinton.

Facing criticism earlier this year for her use of the server, Clinton handed over about 30,000 work-related emails for the State Department to make public and deleted about 31,000 emails she says were personal.

In August, Clinton handed over the entire server to the FBI, which has been able to recover at least some of the deleted emails.

But agents sifting through the emails Clinton said were "personal" in nature have reportedly handed some over to investigators — indicating that they are relevant in at least some way to the FBI's investigation into the server.

In March, a House committee requested access to Clinton's server to ensure that she had not deleted any work-related emails. But her lawyer, David Kendall, told the committee that Clinton aides had changed the server's settings so that only emails she sent and received in the previous 60 days would be saved.

Clinton at a news conference at the United Nations in New York on March 10. REUTERS/Mike Segar Clinton told Todd she had nothing to do with this process, either.

"All I can tell you is that when my attorneys conducted this exhaustive process, I did not participate, I didn't look at them," she said. "If they thought it was work-related, it would go to the State Department."

"My attorney said, 'Well, what do you want us to do with all these personal emails?' I said, 'Well, I don't need to keep them. I don't need them or want them.' So they then talked to the IT server, the technical people who were responsible for maintaining them and said, 'You know, we don't need them anymore,'" Clinton said. "That's the limit of my knowledge.

"There's only so much I can control," she added. "I can't control the technical aspects of it. I'm not by any means a technical expert. I relied on people who were."

Frustrated, she asked Todd whether his next question would be "another conspiracy theory."

The FBI investigation has reportedly centered on 18 US Code 793, a section of the Espionage Act related to gathering and transmitting national-defense information, and is being led by an FBI "A-team" out of its Washington, D.C., headquarters.

Clinton is not the subject of a criminal investigation, and it remains unknown how much classified information was consciously shared over the server.

So far, investigators have not found any emails in Clinton's server that were marked "classified" at the time they were sent or received. But some of the information Clinton shared with colleagues may have been inherently classified, Reuters reported, even if it was not marked as such.

Anyone who inadvertently shared classified information with Clinton via email could face criminal charges and be prosecuted for "gross negligence," Bloomberg reported.