Envelopes containing suspicious powder were sent to three foreign consulates in Manhattan on Monday, but initial tests suggested the mailings were a hoax, police officials said.
A field test done on the powder sent to the Uzbekistan Consulate came back negative for anthrax or any other dangerous substance, New York Police Department spokesman Paul Brown said.
Envelopes containing a powder were also sent to the French and Austrian consulates.
All three envelopes had Dallas, Texas, postmarks, and at least one contained a note referencing al Qaeda, Brown said.
The potential threat prompted an emergency response from federal and local authorities, including hazardous material units that decontaminated employees of the consulates who handled the envelopes.
"The FBI is working with the NYPD to determine the origin of these letters," said Richard Kolko, spokesman for the FBI's New York Office. "Our field office will follow all leads to locate the sender."
Telephone calls to the consulates went unanswered or were not immediately returned.