Mexico's Panamerican University on Monday acknowledged that President Enrique Pena Nieto copied ideas and texts without crediting their authors in his 1991 thesis, confirming earlier reports from the investigative news site Aristegui Noticias.

While the university did not specifically use the word "plagiarism," it did say that his thesis included "textual reproductions of fragments (of other works) without footnotes or mentions in the bibliography."

Nieto's alma mater noted that citation standards had become more rigorous since he attended the university, but noted that "our university's general rules do not apply to ex-students."

"This is an old case which cannot be subject to any action," it said in a statement, adding that it has consulted the National Autonomous University of Mexico, the country's largest, to determine how to proceed in the "unprecedented" case.

According to Aristegui Noticias, 197 out of 682 paragraphs in Nieto's thesis have been plagiarized.

This is not the first time the investigative news site led by Mexican journalist Carmen Aristegui has uncovered misconduct on behalf of the president.

In 2014, it revealed that Nieto's wife purchased a $7 million (6.26 million euros) mansion in Mexico City from a government contractor, which effectively tarnished the president's image across the nation. He acknowledged that he made a "mistake," asking for the country's forgiveness.

The latest controversy surrounding the Mexican president comes as Nieto's popularity has hit an all-time low, with only 23 percent support from the population, according to the latest poll published Mexico's "Reforma" newspaper.

ls/gsw (AP, AFP)