People who were there described seeing police dogs around the event, as well as officers on the roof of the building, apparently looking for people smoking marijuana.

The arrests outraged event organizers, and some attendees said they left patients frightened as Nevada's first legal dispensaries prepare to open.

"It's disheartening for our whole community," said Jennifer Solis, who's with Wellness Education Cannabis Advocates of Nevada, or WECAN, and was at the event.

From Friday to Sunday, officers shut down five booths, arrested 10 people and cited three others on charges including drug possession, possession with intent to sell and transporting a controlled substance, said officer Laura Meltzer, a Metro spokeswoman. She said officers seized marijuana, hashish, marijuana seeds, edible products containing THC and psilocybin mushrooms.