The National September 11 Memorial & Museum plaza was evacuated briefly Sunday afternoon after visitors reported a chlorine-like smell and fumes coming from one of the site's two fountains, the FDNY said.

A chemical substance used to clear green algae from the south fountain was believed to be the cause of the strong odor, FDNY spokesman Lt. Craig Mosia said.

A HAZMAT team and the city's Department of Environmental Protection were dispatched to the area shortly after 2 p.m., and the site remained off-limits to the public until about 4:40 p.m., Mosia said.

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Michael Frazier, spokesman for the memorial and museum, said in an email the site was closed as a precaution.

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"It was determined by the authorities that what memorial visitors smelled posed no health or safety risks and operations have resumed," Frazier wrote.

No one at the site required medical attention, authorities said.

The incident occurred two days after the museum celebrated its first anniversary. A statement on the museum's website says 2.7 million visitors have been to the museum since it opened on May 15, 2014.