WASHINGTON — Defense Secretary Ashton B. Carter continued to use a personal email account for government work for at least four months last year after the White House questioned the Pentagon about why he was using it, according to copies of Mr. Carter’s emails released by the Defense Department on Friday.

The New York Times reported in December that Mr. Carter had relied on the account at least through May, two months after the newspaper reported that Hillary Clinton had exclusively used a personal email account when she was secretary of state.

According to the emails released on Friday, Mr. Carter continued to use the account for government work at least until September. Mr. Carter said in December he had made a mistake in using the account. Since 2012, the Defense Department has prohibited its employees from using personal email accounts for official work.

The Pentagon released 1,336 pages of Mr. Carter’s emails and attachments on Friday in response to Freedom of Information Act requests by The Times and other news media outlets.