Ten students were being treated after ingesting an unknown substance at James Lick Middle School in San Francisco.
School staff called 911 about 1:20 p.m. after several students showed "adverse effects" from the substance, Lt. Jonathan Baxter, a spokesman for the San Francisco Fire Department, told reporters. The students ranged in age from 12 to 15.
One student became extremely ill, while two others had moderate symptoms, including vomiting and an altered level of consciousness, Baxter said. Seven students had minor symptoms and were being taken to hospitals for evaluation.
Although students told officials what they thought they ingested, authorities could not confirm the substance involved. The investigation is ongoing.
Parents were asked to come forward if their children exhibited unusual behavior or admitted to ingesting the substance.
"They will not be in trouble," Baxter said.