Ten students were evaluated Thursday morning after a suspected cannabis overdose at a middle school in California’s San Fernando Valley.

Around 11:20 a.m., Los Angeles firefighters responded to Van Nuys Middle School, officials said in an alert.

The students, who are 12 to 15 years old, were found to be in “mild-to-moderate distress,” fire officials said in an updated alert. The students appeared lethargic and had a glazed-over look, authorities said.

Seven were taken to local hospitals that specialize in pediatric medicine, while three were released at the scene.

Christopher Angel, 12, told the Los Angeles Times that three people in his class were affected.

“They were acting weird, tired, high,” he said.

The school was searched for any additional victims, but all students were accounted for. Parents were seen rushing to the school to make sure their children were unharmed.

The incident was not fentanyl-related, crews at the scene confirmed, but they said it could possibly be related to edible cannabis. Fentanyl is a highly addictive and potentially lethal drug. Paramedics did not administer the opioid overdose-reversing drug naloxone, officials said.

Hospital personnel will determine which possible substances were used, officials said, and investigators were trying to determine whether all 10 students got the substances from the same source.

Video from the scene showed a large police and fire presence as students were wheeled out of the school and put into ambulances.

Authorities are still investigating how the substance made its way onto campus and into the hands of students.

In a statement, the Los Angeles Unified School District said medical assistance was requested “in an abundance of caution” but that the campus remained “safe and open for instruction.”