(RNN) - The U.S. Park service is investigating how a noose came to be placed inside the Smithsonian National Museum of African American History and Culture in Washington, D.C.
The noose was found Wednesday, four days after another noose was found hanging from a tree outside the Hirshhorn Museum, an art museum beside the National Mall.
"The noose has long represented a deplorable act of cowardice and depravity - a symbol of extreme violence for African Americans," Lonnie Bunch III, director of the black history museum, tweeted. "Today's incident is a painful reminder of the challenges that African Americans continue to face."
Smithsonian officials reopened the exhibit gallery within three hours and assured the public that the museum is safe.