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WEST FARMS, Bronx — A janitor found a knife in the back of the classroom where a teen was fatally stabbed one day later, spokespeople for the school safety-agents union confirmed.

A janitor found this knife in the back of the Bronx classroom where a student was fatally stabbed.

The employee turned the knife over to the NYPD after the discovery.

Detectives conducted an investigation and determined that the knife was not associated with the stabbing incident at the Urban Assembly School for Wildlife Conservation in the Bronx , police said.

Metal detectors were quickly installed at the school after the fatal Sept. 27 stabbing.

Abel Cedeno was able to bring a 3-inch switchblade into the school. He allegedly used it to fatally stab one teenage boy in the chest and seriously injure a second teen. Cedeno allegedly told investigators he bought the switchblade online about two weeks ago.

Cedano was charged with murder, two counts of attempted murder, manslaughter, two counts of attempted manslaughter, two counts of assault, two counts of criminal possession of a weapon.

An Education Department spokesperson declined to comment on the discovery of the second knife.