OKLAHOMA CITY (AP) — Authorities say they've arrested a teen who fled an Oklahoma City high school after dropping a backpack with a loaded gun inside.

Oklahoma City Public Schools spokeswoman Beth Harrison tells The Oklahoman that a former student entered U.S. Grant High School Thursday but was stopped by staff members.

Oklahoma City police Capt. Bo Mathews says the 16-year-old may have entered the building through a side door that had been propped open. The school's front entrance is equipped with a metal detector.

The school was placed on lockdown as authorities searched for the teen. The boy fled the area after being spotted on campus.

No shots or injuries were reported.

Mathews says the boy was later taken into custody in another city on two felony robbery warrants.