PHILADELPHIA (CBS) — A Philadelphia middle school was placed on lockdown on Tuesday afternoon after a student observed another student with a gun in his backpack, police say.

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Officials responded to reports of person with a gun shortly before 2 p.m near Woodrow Wilson Middle School shortly along the 1800 block of Cottman Avenue.

One person was taken into custody.

Lee Whack, a spokesman for the Philadelphia School District, told KYW Newsradio 1060 that the middle school was placed on lockdown due to a possible weapon in the building.

“The School District and the Philadelphia Police Department are taking all the necessary precautions to investigate the situation and make sure students are safe,” said Whack.

Police did not recover a firearm, which they believed was tossed in the sewer.

The lockdown was lifted shortly before 5:30 p.m.