(CNN) The use of personal email to conduct government business has yet another Obama administration official under scrutiny.

The New York Times reported Thursday that Secretary of Defense Ashton Carter did so for part of his official work in the first months after taking on his duties, referring to emails it had obtained copies of.

The Defense Secretary reportedly kept using private email after news about Hillary Clinton's use of a personal email server during her service as secretary of state triggered attacks by Republican lawmakers.

Carter told reporters traveling with him in the Middle East Thursday that he had made a mistake and ended the practice a few months ago.

"Someone in my position should have known better. I did not do the right thing," he said.

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