A shipment containing 16 kilogrammes of cocaine was seized last week at the UN's mail intake centre.
Paul Browne, New York Police Department's (NYPD) chief spokesman, said the drug was in a white bag evidently masquerading as a diplomatic pouch that raised suspicions when it was being scanned because it was stamped with what looked like a poorly concocted version of the UN logo.
Mr Browne said there was no name or address on the shipment sent from Mexico City through Cincinnati.
UN security officials called the NYPD and Drug Enforcement Administration, which confirmed the substance inside the shipment intercepted January 16 was cocaine, the police spokesman said.
UN under-secretary-general for safety and security Gregory Starr told reporters that "there is nothing to indicate that this had anything to do with anybody at the United Nations".
Mr Starr said the drug was actually stashed in two bags that were stamped with the sky-blue UN logo of a world map in an apparent effort to masquerade as diplomatic pouches, which are not supposed to be inspected.
Inside the bag, the drug was hidden in hollowed-out notebooks, he added.
The UN official showed journalists a photograph of the bags that were seized, and compared them with a real diplomatic pouch used by the UN, which is somewhat larger and made of a different material.
"This did not come from a United Nations facility," Mr Starr said of the shipment. "It was not, in my opinion, not intended to go to a United Nations facility."