The landmark 39-story Secretariat building overlooking the East River is under renovation but the Security Council has been meeting in the basement. The adjoining General Assembly building is still being used, ahead of its overhaul.
U.N. security officials initially feared the odor was caused by a gas leak, but the source turned out to be a disruption in the basement sewage system caused by a high tide on the adjacent East River.
"This is not a hazard, there were gases released by the sewage but it is not harmful," U.N. deputy spokesman Farhan Haq told reporters. "Public tours and General Assembly meetings should be able to resume by tomorrow."
Haq had no specifics on exactly how the high tide disrupted the sewage system or whether waste was spilled, but said "the cleanup is ongoing."
The temporary four-story building constructed on the north lawn of the U.N. complex, where Secretary-General Ban Ki-moon has his offices, was also briefly evacuated.
But U.N. staff and diplomats were allowed to return and the Security Council and General Assembly meetings were moved to conference rooms in the north lawn building.
The evacuation delayed a morning Security Council event for members to hear the views of young people, including 150 New York City students, planned by U.S. Ambassador Susan Rice, in her capacity as this month's council president. It also delayed General Assembly action on dozens of pending resolutions on human rights.
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