Guttenberg resigned in March and admitted to errors in his dissertation – but rejected claims that he had intentionally plagiarized or sought to deceive his alma mater.
Daily Süddeutsche Zeitung said a commission at the University of Bayreuth determined that the extent and manner of the infringements were such that they could not have been inadvertent.
Guttenberg was officially stripped of his doctor title in February. "The committee is unanimously convinced Herr Baron zu Guttenberg seriously violated scientific duties," said University President Rüdiger Bormann at a press conference.
The University of Bayreuth has yet to publish its findings. The commission, which includes professors from other colleges, is not yet completely finished with the report, and some editing is set to continue until the end of April.
According to the Nordbayerische Kurier, the university plans to release the commission's findings early next month.
Meanwhile, Süddeutsche Zeitung reported that lawyers representing Guttenberg have expressed "reservations" about the review being published.
Speaking to Berlin daily Tagesspiegel, Bormann confirmed that the university had received the lawyers' letter and said the university would not release the report if Guttenberg still opposed it, adding that the review was an internal procedure.
But he expressed hopes that the ex-defence minister would change his mind: "We would like to publish the findings – including those concerning the issue of fraudulent intent." Bormann said keeping the report under wraps ran counter to Guttenberg's pledge to investigate the issue.
State prosecutors looking into potential infringements against copyright law have also made it clear they were interested in soliciting the university's report and using it in their investigations.