USC President Carol L. Folt confirmed Wednesday that police investigators are looking into drug overdoses as a potential cause of death among some of the nine students who have died this semester.

While Folt would not elaborate on the scope of the inquiries or circumstances of the individual deaths, citing federal student privacy laws, she said USC is working with the Los Angles Police Department on the cases and “doubling down” on education and outreach over drug abuse.

Three of the nine deaths have been ruled suicides, but the cause or causes in the remaining cases have not been officially determined.

Investigators are trying to determine whether any student deaths are connected with tainted drugs, said sources who spoke to The Times on the condition on anonymity because they were not authorized to comment. The sources stressed that no links to tainted drugs have yet been confirmed. Autopsies and toxicology tests are still pending in a number of the deaths.

“We’re doubling down on educating [students] about the harm and serious risks associated with all types of drug abuse and substance abuse,” Folt said Wednesday. “And in particular, we’ve been also talking about the real risks of mixing opioids and prescription drugs and alcohol because we are concerned about that.”

In a letter sent to staff and students just after 10 p.m. Tuesday, top USC officials warned against the dangers of drug use — specifically opioids — and the sometimes lethal mixture of drugs and alcohol. The statement further warns about the increase of contaminated drugs.

“We all know that people that get drugs on the street have no idea what is in those drugs,” Fold said.

According to the U.S. Centers for Disease Control and Prevention, deaths from drug overdoses have increased dramatically across all age groups over the last decade, with opioids and synthetic opioids — such as fentanyl — the main cause.

Fentanyl is a painkiller often prescribed as a skin patch for cancer patients and is considered 50 times stronger than heroin. Illicit fentanyl, manufactured as a white powder, has infiltrated the drug supply and can be lethal even in small amounts.

Last year, 2,311 people in California died of an opioid overdose, according to the state Department of Public Health. Young people are more likely to die from heroin and fentanyl overdoses than older drug users, who more commonly overdose on prescription opioids, state data show.

In 2017, 4,094 people nationwide ages 15-24 died of an opioid overdose, according to the CDC. That same year, the age group with the highest opioid overdose deaths was 25- to 34-year-olds.

USC Police Chief John Thomas said the university decided to relay the new information to students for their safety. Officials wanted to warn them about the dangers of narcotics and improperly used prescription medications in light of the deaths.

“You [students] may feel invincible, but you are not,” Thomas said. “Please look out for yourself and your fellow students.”

The threat and danger of tainted drugs on college campuses is widespread, according to Dr. Caleb Alexander, co-director of the Johns Hopkins Center for Drug Safety and Effectiveness.

Counterfeit pills often contain fentanyl, which is added to the drugs to give them a stronger high.

In 2016, 28 people in Sacramento overdosed on counterfeit Norco laced with fentanyl, and several died.

In recent years, public health officials have become concerned about what they see as the latest phase of the opioid epidemic: non-opioids, such as cocaine or ecstasy, that contain deadly fentanyl.

While the West Coast has been somewhat spared from the worst of the opioid epidemic, many worry that fentanyl-laced drugs could become a major problem in California because the state’s drug market is dominated by stimulants that could increasingly contain fentanyl.

“The presence of fentanyl in cocaine and other non-opoid drugs represents an extremely difficult and serious problem for public health authorities and for drug users alike,” Alexander said.

Putting fentanyl in a drug like cocaine greatly increases the risk of death, experts say. Last year, three men in Los Angeles died after snorting cocaine that contained fentanyl. And in September 2018, rapper Mac Miller died of an alcohol and drug overdose of cocaine and oxycodone pills laced with fentanyl.

“There are a tremendous number of unanswered questions regarding why and how this is taking place,” Alexander said. “The prospect for fentanyl to further penetrate the non-opioid drug supply is incredibly serious.”

Though little is known about the specific deaths, risk factors for suicides and overdose deaths can be similar, with both often driven by an ambivalence about life, said Dr. Paul Nestadt, a Johns Hopkins psychiatry professor. And suicides and overdoses have been increasing among young people in recent years, he said.

“They’re both kind of going up at the same time, almost twin epidemics,” he said.

Between 2006 and 2016, the rate of drug overdose deaths among people ages 15 to 24 increased more than 50%, according to CDC data. Still, the rate of drug overdose deaths for this age group was lower than all others, except those under 15 and over 65.

And drug use can be further exacerbated by alcohol abuse. Alcohol and opioids are both sedatives, and mixing them can be a dangerous combination, said Alexander. Both substances depress the body’s central nervous system, which can halt breathing and be fatal, he said.

It’s not uncommon to find alcohol in the bloodstream of someone who has died of an opioid overdose, Alexander said.

“The deaths are very alarming. There’s no corner of the U.S. that’s been spared from the opioid epidemic, and college students are clearly vulnerable.”

Among the USC student deaths, all are men. Rates of drug overdose — as well as suicides — are higher among men than women, although experts are not sure why.

USC administrators have been engaged in a delicate balancing act as they notify students about the deaths without overburdening them with information in an attempt to quell rumors, offer mental health resources and also try to avoid triggering anyone who may be in the midst of a mental health crisis.

In the letter sent Tuesday night to USC students, Vice President for Student Affairs Winston Crisp and Chief Health Officer for Student Health Sarah Van Orman addressed the ongoing need for mental health services and noted the university’s plans to increase resources on campus with the addition Monday of a Department of Psychiatry practice at the student health center.

“We will continue to ensure that services are in place for your safety and well-being.”

Brittney Weissman, executive director of the National Alliance on Mental Illness Los Angeles County Council, said that emphasizing social connectedness will be essential for the USC community.

In general, support systems are vital because college is a transitional period and people may feel a lot of pressure to succeed, she said. And now, as students are dealing with the trauma of the recent deaths, those bonds are more important than ever.

“I cannot imagine losing nine friends or classmates in the span of months,” she said. “It’s devastating.”

Weissman said that students should pay attention to their anxiety levels and use self-care strategies and that officials should ensure mental health resources are available to students, with no barriers.

Folt said USC has increased the number of mental health professionals by nearly 50% since she arrived on campus in July.

“No death is something we want to live with and no unhappy student that cannot get their work done is what we want,” she said. “So constant, constant attention is needed. “

Officials said additional resources from faculty and counselors at Keck Medicine School and other schools across the university are offering assistance, as the community continues to grapple with the deaths.

Weissman said students who are struggling may become withdrawn or engage in risky behaviors. People may stop their daily routines, such as going to class, showing up to sports practices or brushing their teeth.

Half of a person’s mental health challenges show up by their 14th birthday, Weissman noted, and 75% by age 24. So college can be the perfect time to start seeking help, she said.

“Early intervention is key to a more positive trajectory for your life,” she said. “The earlier, the better.”