An explosive device was lobbed over a backyard fence west of Sierra High School at 11:15 Friday night where some 60 teens were having a Fourth of July party – injuring six between 15 and 18 years old, according to police.

Officers arrived on the scene and discovered most of the victims had already been transported to an area hospital by friends as police secured the scene.  A black car, possibly a Honda Accord was seen traveling away from the home northbound on Fishback Road, police said.

Lt. Tony Souza said the students were in a circle when the device fell between them and exploded at chest high.  One victim was airlifted by helicopter to a Bay Area hospital with an eye injury. Another teen also received a serious injury from the explosion.

Members of the Manteca Police Investigations unit and Bomb Squad were requested to assist in the investigation.  Anyone with information pertaining to this case is urged to contact the Manteca Police Department at 209.456.8101.