At least 10 San Francisco middle school students sickened by mystery substance

SAN FRANCISCO (Reuters) - At least 10 students at a San Francisco middle school underwent medical treatment on Tuesday for exposure to an unknown substance, possibly an illicit drug, that some of the youngsters appeared to have ingested, emergency and school officials said.

Details of the incident at James Lick Middle School in the city's Noe Valley neighbourhood remained unclear, but San Francisco television station KRON-TV reported that five of the students were hospitalized and that one of the 10 students was listed in critical condition.

A citywide red alert was activated, allocating all available ambulances to the location of the school, media reports said. The school has about 550 students enrolled in sixth, seventh and eighth grades, CBS affiliate KPIX-TV said.

At least 10 students were treated after exposure to what may have been an illicit drug, said Ethan Baker of the city's Emergency Management Department.

"At this time it appears as though some students have ingested a substance that is causing adverse reactions," the San Francisco Unified School District said in a separate statement. It said the families of the affected students are being contacted.

(Reporting in San Francisco by Heather Somerville and Jim Christie; Writing and additional reporting by Steve Gorman in Los Angeles; editing by Grant McCool)