Mississippi police are investigating seven nooses and six “hate signs” found in the grounds of the state legislature, a day before a US Senate vote that has focused attention on the area’s history of racist violence.
It was not immediately known who put the nooses up or why.
Chuck McIntosh, a spokesman for the Mississippi Department of Finance and Administration, which oversees the state capitol building, said the nooses and signs were found shortly before 8am on Monday on the south side of the site in central Jackson.
He said the matter is under investigation by the Mississippi Capitol Police.
Mississippi is preparing for a US Senate run-off on Tuesday between Republican senator Cindy Hyde-Smith and Democrat Mike Espy in a contest that has increasingly taken on racial overtones.
Ms Hyde-Smith, who is white, has drawn fire for a photo showing her wearing a replica hat of a Confederate soldier, and a video showing her praising a supporter by saying: “If he invited me to a public hanging, I’d be on the front row.”
Mr Espy is seeking to become the first African-American US senator from Mississippi since Reconstruction.
Neither candidate has commented on the nooses.
The president said she has apologised and misspoke, adding that her comments were “taken a certain way but she certainly didn’t mean it”.
The NAACP website says that between 1882 and 1968, there were 4,743 lynchings in the United States, and nearly 73% of the victims were black. It says Mississippi had 581 during that time, the highest number of any state.
Civil rights activists were beaten and killed in Mississippi as they pushed for African-American voting rights, particularly from the end of the Second World War until the 1960s.