"There is no immediate risk or danger," U.N. deputy spokeswoman Marie Okabe said.
She said there was no evacuation of the office of the U.N. Monitoring, Verification and Inspection Commission, known as UNMOVIC, about a block north of U.N. headquarters on New York's east side, and U.S. authorities were called in to dispose of the material.
Okabe said one of the substances, identified Wednesday, was phosgene suspended in oil, "whose present state is unknown but which could be potentially hazardous."
Phosgene can be used as a chemical weapon - and was used extensively in World War I - as a choking agent. Both phosgene gas and liquid can damage skin, eyes, nose, throat and lungs.
UNMOVIC spokesman Ewen Buchanan said the phosgene was in liquid form, suspended in the oil, in a soda-can-sized container. It was found in a sealed plastic bag that included "unknown liquid substances contained in metal and glass containers ranging in size from small vials to tubes the length of a pen," she said.
"The only information we have of the contents of that bag is from an inventory of a 1996 inspection, which indicates that one of the items may contain phosgene, an old generation chemical warfare agent," Okabe said.
Okabe said the material was immediately secured by UNMOVIC experts and the U.N. sought assistance from U.S. authorities in having the material safely removed. The U.N. was informed that the FBI was going to the office Thursday to remove and dispose of the material, she said.
"The office area was screened using UNOMVIC's chemical weapons detection equipment. No toxic vapors were found. There is no immediate risk or danger. UNMOVIC staff are still working on the premises," Okabe said.
Buchanan said a second sealed package contained tiny samples of chemical agents in sealed glass tubes shaped like pens that are used by inspectors to identify chemical agents. Each of these reference standards contained less than a gram of chemical material, he said.
Buchanan said the material was discovered Aug. 24, put in double zip-locked bags, and locked in a safe in a room that is double-locked. The only marking on the material was an inventory number, he said.
UNMOVIC has 1,400 linear feet of files, and it took until Wednesday to find the inventory the number matched which indicated that the material was from Iraq's main chemical weapons facility at Muthana, near Samarra.
The State Department said it had learned of the discovery late Wednesday and had immediately contacted the FBI to deal with the disposal.
Deputy spokesman Tom Casey also said a joint U.S.-U.N. investigation would be made into why the samples had been stored in the office but stressed that the chemicals had been there for at least a decade and did not pose any health risk.
"One of the things we want to do is make sure that the U.N., working with the FBI, does conduct a full investigation of this, so we're absolutely certain how they in fact got there, how long they were there, and the kind of exact nature of how this came about," he told reporters.
"There is no threat that these items currently or in the past have posed to public health and safety in the area," Casey said.
White House press secretary Tony Snow said the chemical agents "were brought over as a result of U.N. weapons inspections during the UNMOVIC era" and had been at the UNMOVIC facility for over a decade.
"They've done some testing of the air, and there's no danger to the folks involved," Snow said.
The agents should have been transported to an appropriately equipped lab for analysis, he said, adding: "I'm sure that there are going to be a lot of red-faced people over at the U.N. trying to figure out how they got there."
U.N. inspectors pulled out of Iraq just before the March 2003 U.S.-led invasion and were barred by the U.S. from returning. The U.S. and Britain said they were taking over responsibility for Iraq's disarmament. In June 2003, the Security Council voted to shut down UNMOVIC and the U.N. nuclear inspection operation in Iraq.
Okabe said the United Nations has launched an investigation to determine how and why the material was in UNMOVIC files.
Brian Mullady, a senior UNMOVIC official, told reporters that the staff did an immediate sweep of the rest of its archives to see if there was any more material but there was none.