Hillary Clinton Addresses Concerns Over Email Server ... In An Email

"I'm sorry about it, and I take full responsibility."

WASHINGTON -- Hillary Clinton sent her supporters an email late on Tuesday apologizing for her use of a private email server while serving as secretary of state.

"Yes, I should have used two email addresses, one for personal matters and one for my work at the State Department. Not doing so was a mistake. I'm sorry about it, and I take full responsibility," Clinton wrote in the email.

The Democratic presidential contender stressed that she plans to fully cooperate with the ongoing federal investigation. Previously, she authorized the State Department to release the 55,000 pages of her emails, which were rolled out in batches starting in May and will continue to be released until January. Clinton will also testify before the House Benghazi Committee on Oct. 22.

"As this process proceeds, I want to be as transparent as possible," she wrote in the email.

Clinton added that her private server "was aboveboard and allowed under the State Department's rules" and that government officials who received emails from her private account were "aware of it." She also said none of the emails contained information that was considered classified at the time, though some of the emails were later found to have contained classified material.

The candidate conceded that she has played a role in furthering the controversy by repeatedly shrugging off the issue and refusing to address questions about it.

"I could have -- and should have -- done a better job answering questions earlier," she wrote.

The campaign posted the text of Clinton's message to Facebook and provided supporters with more information on her website, including a link to the emails themselves.

Earlier on Tuesday, Clinton issued a similar apology in an interview with ABC News, saying, "That was a mistake. I'm sorry about that. I take responsibility." However, she declined to apologize as recently as Friday.