The FBI and police are investigating suspicious letters filled with white powder that were sent to three foreign-government missions at the United Nations in New York on Monday.
The letters appeared at the missions of France, Austria and Uzbekistan, police said.
As a precaution, 15 people were decontaminated at the French mission, three at the Austrian mission and two people at the Uzbekistan mission.
Early tests on the white powder came back negative for anthrax or other dangerous substances, police said.
The envelopes were all postmarked from Dallas.
No one was injured and the missions did not need to be evacuated, police said.