SAN FRANCISCO—A celebration at Golden Gate Park on Friday, April 20 left over a dozen people hospitalized. The event took place at a zone known as Hippie Hill in honor of 4/20. Officials from the San Francisco Police Department are investigating the cause that led multiple individuals to become ill. The incapacitated partygoers consumed edibles that were laced with more than the marijuana. According to reports, fentanyl may be responsible for the hospitalizations. It is illegal in the city of San Francisco to sell laced good.

KPIX5 News reported seeing a patient being treated with Narcan before getting carted away in the ambulance. Narcan has been popularized by medical responders and police officers to treat individuals who have overdosed on drugs. Several ambulances converged on the party grounds, where over 20,000 people were in attendance, a large increase from the event in 2017.

Authorities have confirmed that UCSF treated two patients who overdosed at the event from an unknown substance. The San Francisco Department of Recreation and Parks noted that over 20,000 people were in attendance at this year’s event, an increase of 5,000 from the previous year.

The event organizer Alex Aquino, who is the co-owner of the clothing store Black Sale on Haight Street, ensured additional clean-up crews were on hand at this year’s ceremony to clean up trash left behind by attendees.