The African Burial Ground Monument in Lower Manhattan, a treasured site for the nation’s black community, was defaced with a racist slur on Thursday, the authorities said.

In black marker, a vandal scrawled “Kill,” followed by the slur, on a plaque at the monument. The authorities said they did not have a suspect in the incident.

Discovered in 1991 during construction of an office building, the six-acre burial ground is estimated to contain 15,000 intact skeletal remains of New York City’s colonial African-American community, who were not allowed at the time to be interred in traditional church cemeteries. Many were slaves.

The monument, which is steps from City Hall, is considered a literal and figurative symbol of New York’s prominent and long-ignored role in colonial African-American culture.