FILE - In this March 12, 2019, file photo, people pose for photos in front of the iconic Tommy Trojan statue on the campus of the University of Southern California in Los Angeles. The death of nine students since classes began a little more than two months ago has left students and administrators at the University Southern California shaken and seeking answers. The Los Angeles Times reports the latest death was discovered Monday, Nov. 11, 2019, when the body of a 27-year-old student was found in an off-campus apartment. (AP Photo/Reed Saxon, File)

LOS ANGELES (AP) — Police investigators are looking into drug overdoses as a potential cause of death among some of the nine students who have died this semester at the University of Southern California.

USC President Carol L. Folt told the Los Angeles Times on Wednesday that the school is working with police and “doubling down” on education and outreach over drug and alcohol abuse.

A letter sent Tuesday to staff and students warned about the dangers of substance abuse, and especially about the increase of contaminated drugs.

The death of nine students since classes began a little more than two months ago has left students and administrators shaken and seeking answers.

Administrators say three deaths were the result of suicide. The causes of the other deaths are either unknown or haven't been disclosed.

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Information from: Los Angeles Times, http://www.latimes.com/

FILE - This March 12, 2019, file photo shows the University Village area of the University of Southern California in Los Angeles. The death of nine students since classes began a little more than two months ago has left students and administrators at the University Southern California shaken and seeking answers. The Los Angeles Times reports the latest death was discovered Monday, Nov. 11, 2019, when the body of a 27-year-old student was found in an off-campus apartment. (AP Photo/Reed Saxon, File)