The University of Southern California is investigating the death of its ninth student in three months, a phenomenon that's sending alarm throughout the campus community.

Three of the deaths have occurred since Friday.

A 28-year-old student was found dead in off-campus housing on Monday by USC public safety personnel, who were responding to a welfare check. The cause of death has not been released, but the LAPD says no foul play is suspected after the death was reportedly considered suspicious on Monday, according to CBS Los Angeles.

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Just one day before, the university sent a letter to students and parents, acknowledging the then-eight deaths among the student body since late August. The university’s president, Carol Folt, said that many students had been assuming most of the deaths were the result of suicide, which was “not correct.”

“These tragic losses have resulted from a number of different causes. In some cases the cause of death is still undetermined, and in others loved ones do not want details disclosed,” Folt said in the letter. The causes of death vary and some have not yet been determined. At least three were suicides.

In the first death of the semester, freshman Matthew Olson, 18, was hit and killed on the freeway while walking between lanes.

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“We have had a number of student deaths that have happened in a very short period of time,” USC’s chief health officer, Sarah Van Ormon, told CBS Los Angeles. “We are experiencing a lot of speculation on social media. Part of the intent of the letter was to calm some of those fears.”

The university said it typically sees between four and 15 deaths per year in the community of about 47,000 undergraduate and graduate students, according to KTLA.

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USC didn't immediately comment to Fox News.