"I attempted to appropriately cite and acknowledge all sources in America the Beautiful, but inadvertently missed some. I apologize, and I am working with my editors to rectify the situation," Carson said in a statement his representative, Armstrong Williams, provided to CNN.
BuzzFeed News broke the story earlier this week that Carson had lifted material from a number of books and online sources for his 2012 book "America the Beautiful."
Among those sources is SocialismSucks.net, a site whose founder acknowledged to BuzzFeed that Carson had taken some of his comments. Other sources included "The Five Thousand Year Leap" by W. Cleon Skousen, a Liberty Institute press release, CBS News and author William Federer's book "America's God and Country."
Carson, a neurosurgeon who's said he'll make a decision on a 2016 bid by this spring, is the latest GOP presidential contender to be hit with plagiarism charges. Sen. Rand Paul (R-Ky.) faced similar accusations about his own book in 2013.
The plagiarism charges have "blindsided" Carson, a source close to the neurosurgeon reportedly told the National Review Online
"Alongside the author, we too take these matters very seriously. We have been in contact with the author and agent and will work with them to review the given information. We will respond as appropriate," a spokesperson for HarperCollins Christian publishing, which published Carson's book, told BuzzFeed.
Federer, though, told CNN in an email that he'd given Carson permission to use his material -- and he even read and signed off on the final product.
He said he met Carson while the two served on a university board, and handed him copies of his books during a shuttle ride on campus.
"I told him that I hoped he would find them interesting and that he had full permission to use any of the material in the books as he liked," Federer said.
"One of the books I gave him was specifically designed to be quoted," he said, noting that its subtitle specifically says that the material is for use in speeches, papers, debates, essays and articles, including those by elected officials.
He then listed 16 acknowledgments and citations of his work in Carson's book, saying that "it is obvious that Dr. Ben Carson has made demonstrable effort to make proper attribution. Indeed, his overt acknowledgments have resulted in numerous individuals contacting me to purchase the book."
Carson did not immediately respond to request for comment.