MANILA, Philippines – Eighteen persons were hurt after suspected fraternity members threw an explosive at 4:25 p.m. Tuesday outside the La Consolacion College in Mendiola, Manila.

Manila Police District Explosive Ordnance Division chief, Insp. Elias Lagasca Jr., said the victims, mostly students and bystanders, suffered minor injuries. They were rushed to various hospitals in Manila for treatment.

Lagasca said they recovered parts of a grenade and a pillbox that did not explode. Police have yet to determine what kind of grenade was used in the incident.

Witnesses told police that the explosive was thrown by some frat members who were reportedly “angry” at the La Consolacion guards who were allegedly tightening security measures against frat men.