Law enforcement officials say three of five suspicious letters sent to United Nations consulates in Manhattan this week were filled with flour.
The Consulate General of Uzbekistan, along with the French and Austrian missions were sent handwritten letters Monday containing the powdered substance.
The potential threat led to a massive response from the FBI, NYPD and the Fire Department's Hazardous Materials team.
U.S. postal inspectors say all three envelopes had a Dallas, Texas postmark on them.
On Tuesday, the British and German Missions to the UN also received envelopes containing white powder.
The building was not evacuated and no one was decontaminated.
The substances in those envelopes are still being tested.
All of the envelopes are said to have contained a hand written letter, specifically addressed to someone in each office.
Some of the notes mentioned al-Qaida, the FBI and America.
The New York Police Department urged all foreign consulates to be careful with mail and advise them of anything suspicious.
"We have to take threats like this seriously in our post-9/11 world. We have to be particularly cautious. We tell people to look at their world through a prism of 9/11," said Police Commissioner Ray Kelly. "So we have built in a regiment that allows us to respond to these things and to carefully check them out."