A noose was found hanging inside the Smithsonian National Museum of African American History & Culture, NBC 4 reports.

Tourists discovered the noose late Wednesday inside an exhibit on segregation. U.S. Park Police are investigating.

“The noose has long represented a deplorable act of cowardice and depravity — a symbol of extreme violence for African Americans. Today’s incident is a painful reminder of the challenges that African Americans continue to face,” museum director Lonnie Bunch wrote in an email to staff.

The noose was removed and closed the museum for roughly an hour as police investigated the scene.

“It’s very hard. It’s very, very, very upsetting,” tourist Tracy Grant said. “We were very emotional to begin with. This is history. This should not be happening in this day and age.”

The incident comes less than a week after another noose was found on the National Mall. Officials said it was hanging from a tree outside the Hirshhorn Museum and Sculpture Garden.

“We don’t let acts of cowardice like this deter us. We are, if anything, even more vigilant and even more determined to tell this important story,” Kinshasha Holman-Conwill, the museum’s deputy director said.

As of Thursday morning, the museum was reportedly operating as usual.