Seoul National University said Friday that independent presidential candidate Ahn Cheol-soo did not engage in plagiarism during his time as a graduate student at its medical school.

“A preliminary probe found no grounds for us to further investigate allegations of plagiarism against five academic papers authored by Ahn,” a research ethics committee of the state-run university said in a press statement. “The case is therefore closed without a main investigation.”

In a unanimous decision, the panel ruled that four of Ahn’s five papers in question were free of plagiarism, and that one that Ahn had co-authored in 1993 was found to have parts that were plagiarized, but the fault lied with the main author.

The university had launched a preliminary investigation last month following allegations made by Rep. Min Byeong-joo of the ruling Saenuri Party in late October during a congressional hearing.

Rep. Min argued that Ahn had plagiarized five research papers, including the thesis for his master’s degree in 1988 and the doctoral dissertation for his Ph.D. degree in 1991, both of which he received from the university.

The claims were seen as a part of political attacks against the doctor, venture entrepreneur and professor-turned candidate whose best political asset, analysts say, is a clean image.

MBC, a local TV channel, had also aired the allegations during its evening news earlier this month, and it received an official warning from the Korea Communications Commission, a government regulator, for engaging in biased reporting.

By Samuel Songhoon Lee (songhoon@heraldcorp.com)