A noose was reportedly found hanging outside the National Gallery of Art in Washington, D.C. Saturday, the third similar incident in recent weeks.

U.S. Park Police Sgt. Anna Rose told the Associated Press that her agency is investigating the incident.

A noose was found last month in the lobby of the National Museum of African American History and Culture, and another one outside the Hirshhorn Museum. The three museums are located on the National Mall.

The NCAAP condemned the noose found in the African-American history museum and called on President Trump to speak out about it.

The incident comes amid a string of racially charged incidents in the U.S. Two people were charged with hate crimes late last month after allegedly hanging a noose at a middle school in Maryland. Another noose was discovered in the Port of Oakland in California.

In May, bananas were found hanging from nooses on American University's campus the same day as the first black woman in the university's history took office as student government president. The FBI announced it was assisting the university to investigate the matter.