This story has been updated. 

UPDATE: 6:00 p.m. EDT: Michael Frazier, a spokesperson for the 9/11 memorial told International Business Times the site was reopened. 

"As a precaution, the FDNY [Fire Department of New York] temporarily suspended operations on the Memorial plaza after a complaint of an odor," he said. "It was determined by the authorities that what Memorial visitors smelled posed no health or safety risks and operations have resumed. The odor was believed to be decomposing algae." 

Original article below.

Sightseers were evacuated from New York City’s 9/11 Memorial Sunday afternoon amid reports of too much chlorine in the two large pools built on the spot where the World Trade Center’s twin towers once stood. Hazmat teams responded to reports one of the fountains was emitting a “foul odor” likely due to the chemical agents used to clean them, WPIX-TV, New York, reported.

The memorial site and museum, which marked their  one-year anniversary Friday, pay tribute to the 2,983 people killed during the attacks of Sept. 11, 2001, and February 26, 1993.

The twin reflecting pools were created by architect Michael Arad and landscape architect Peter Walker. Each pool is roughly an acre in size and feature the largest manmade waterfalls in North America, the memorial’s website says. They feature the names of every person who died in the two attacks, engraved in bronze panels around the edges. 

Roughly 2.7 million visitors from all 50 states and more than 150 countries have come to the site since it opened May 15, 2014. 

Visitors have taken to social media to document Sunday’s evacuation. There are reports all visitors were told to leave the site, and some were seen coughing due to the chlorine in the air.