"It's usually if someone gives you a drink or if they're mixing a lot of stuff and you can't tell what's in it. That's probably what happens," said UCSC student Isabelle Cuttress.
UC Santa Cruz police say it was the likely scenario when three female students were drugged at separate off-campus parties. It happened over a two week period and one of the students was sexually assaulted.
"They felt different. They felt they had been intoxicated at a faster rate. Some of them got sick and vomited," said UC Santa Cruz Police Chief Nader Oweis. "They get one beer and that one beer feels like they had four beers. That's how they get sick."
"I actually have a friend who said something was tainted with her drink on the night of Halloween," said UCSC student Jessica Singer. "But what I thought was interesting was that she was walking when she came to, and she wasn't passed out somewhere."
When asked if her friend reported this incident to police Singer said, "Not that I know of... no."
That means there could be more unreported cases. Still, UC Santa Cruz police believe students are becoming more open to reporting these incidents because of a recent campaign they've been pushing.
"What to do if something happens. See something. Say something. Do something. All of that has been part of our campaign," said Oweis.
And students say they're paying more attention to the advice.
"They said to not leave our drinks, even if we're going to the bathroom. It's like you either drink it or you throw it away," said UCSC student Valerina Inoscencio.
Police say the drugs already passed through the victim's bodies after they reported it, so they don't know what drugs were used. So far, no one has been arrested.
University police posted a message on the department's website urging students to be cautious at parties, in bars and elsewhere, and to never drink anything out of a common punch bowl.
Police also warn students not to leave their drinks unattended, not to accept open beverages from anyone they do not know well and trust and to remember that many drugs placed into drinks are colorless, odorless and flavorless.
"If someone offers to buy you a drink, go up to the bar with them and accept the drink," Oweis said.
Bay City News contributed to this report.