Three students at Sunnymead Middle School in Moreno Valley were hospitalized Wednesday after ingesting food containing marijuana, the Riverside County Sheriff’s Department said.

Fire officials responded to the school, located at 23996 Eucalyptus Ave., around noon after receiving reports that four students had possibly overdosed on an unknown substance.

Three of those students were transported to a local hospital with symptoms including an “upset stomach, vomiting and pale complexion,” Riverside County Sheriff’s Sgt. Deirde Vickers told KTLA. Another student was treated at the school.

Authorities later confirmed the substance was edible cannabis.

“It is unknown if the substance was obtained from others on campus or whether it was brought on campus from an outside source,” Vickers said.

Last week, ten students at Van Nuys Middle School were treated for mild to moderate symptoms after ingesting marijuana edibles, the Los Angeles Fire Department said.

Experts say emergency rooms across the nation have seen a growing number of cases involving marijuana edibles in recent years, especially in states where cannabis is legal and particularly among preteens and teens.