Eighteen students have received minor injuries when they were exposed to a "loud explosive device" at a school in Southern California.

Authorities couldn't provide further information about the blast. Riverside County firefighters were called at 11 a.m. Friday to Ethan Chase Middle School in Menifee, a city of more than 80,000 about 80 miles southeast of Los Angeles.

The injured students are being screened and released to parents or transported to local area hospitals.