Authorities increased security at Passaic High School on Thursday following a social media threat.
The unfounded post said: "I'm shooting up PHS @2:30 on the set."
Passaic police were joined at the school by Passaic County sheriff's officers.
A lockdown wasn't considered necessary and classes were conducted as usual, authorities said.
They also emphasized that social media chatter Thursday afternoon about a shooting was erroneous.
The Passaic County Prosecutor's Office was investigating along with city police.
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