The United Nations found vials of a chemical warfare agent, which had been removed from Iraq a decade ago, in a UN building near the body's headquarters in New York.
The FBI was called in to remove the substances, which were discovered last Friday and included phosgene, an older generation chemical warfare agent, taken in 1996 by inspectors from a former Iraqi chemical weapons plant at Al Muthanna, the the inspectors said in a statement.
Phosgene was used extensively during World War I as a choking agent, according to the US Centers for Disease Control.
The inspectors, who are closing down their offices several streets from UN headquarters, discovered two small plastic packages with metal and glass containers, ranging in size from small vials to tubes the length of a pen with liquid substances, their spokesman, Ewen Buchanan, said.
Experts sealed the packages and then isolated them in a secured room.
They also tested the area "and found no concentration of toxic vapors in the air," Mr Buchanan said.
The experts, from the UN Monitoring, Verification and Inspection Unit, known as UNMOVIC, believe "the packages are properly secured and pose no immediate risk or danger to the immediate public," Mr Buchanan said.
He said there was no evacuation of staff at UN headquarters and other surrounding offices.