Police say a gun went off during a fight at a Philadelphia high school, but no one was injured.

Police spokeswoman Officer Tanya Little says the gunshot was fired just before noon Friday at Benjamin Franklin High School as students fought in a stairwell.

A search turned up a bullet casing but not a weapon.

Little says the school was placed on lockdown and officials are going room to room looking for the student who has the weapon.

She says no other schools nearby were locked down.

No other information was immediately available.