Democratic U.S. presidential candidate Hillary Clinton speaks to supporters in Winterset, Iowa, July, 25, 2015.
Democratic U.S. presidential candidate Hillary Clinton speaks to supporters in Winterset, Iowa, July, 25, 2015.

U.S. Democratic presidential candidate Hillary Clinton said Saturday that she never used her personal email account to receive or send classified information as secretary of state.

"I am confident that I never sent nor received any information that was classified at the time it was sent and received," Clinton said during a campaign appearance in Iowa, the north-central U.S. state that will hold the first caucuses of the 2016 campaign.

The email controversy has dogged Clinton's bid for the presidency, fueling worries that the front-runner for the Democratic nomination has tried to sidestep transparency and record-keeping laws.

An Iowa Republican Party official said voters do not trust Clinton. He accused her of being less than truthful about what he called her "cavalier handling of sensitive information."

The U.S. Justice Department is considering an investigation into a possible compromise of sensitive information in Clinton's emails but said it would not be a criminal probe.

In a letter to Congress, two federal inspectors general wrote that a review of a "limited sampling" of Clinton's emails found at least four contained classified information that should not have appeared in a private email.

Clinton said Saturday that she had "no idea" what was in the emails mentioned in the letter.

State Department spokesman Mark Toner said some of the emails did not need to be classified at the time they were sent, but have since been re-examined and upgraded as classified.

Clinton has authorized the State Department to make 55,000 pages of emails in her private account public.

She denies doing anything wrong and has said it was more "convenient" to use one email account and one device when she was secretary of state.

"Looking back, it would have been better if I had simply used a second email account and carried a second phone," Clinton said in March. "But at the time, it didn't seem like an issue."

Critics have accused her of trying to hide controversial communications in her private account, including those surrounding the deadly terrorist attack on the U.S. Consulate in Benghazi, Libya, in 2012.

Officials with the Clinton campaign are negotiating with congressional Republicans on terms of her possible testimony before a House committee investigating Benghazi.

Some information for this report came from Reuters.