(CNN)-- Police say a novelty or inert grenade was responsible for the evacuation of a Manhattan skyscraper across the street from the former World Trade Center, the site of the September 11, 2001, terror attacks.
Authorities have since given the all-clear at Two World Financial Center after a bomb squad investigated the incident, according to police spokesman Brendan Ryan.
The "grenade-like novelty item" was "mounted on a plaque with a sign: "Complaint Dept. Pull Pin," according to the NYPD's official Twitter account.
The package was flagged in the building's mail room at 10:53 a.m. when it was scanned, said police spokeswoman Kim Royster. The building's security personnel initiated the evacuation about seven minutes later, she said.
Construction is well under way on One World Trade Center, which is being built near the imprint of the twin towers that fell more than 10 years ago when hijacked planes crashed into them.