A hangman's noose was pinned up on the office door of a black professor at New York's Columbia University, once again flaring up the deap-seated racial issue in the United States, media reported Thursday.
The professor, Madonna Constantine, arrived at work on Tuesday to discover the noose outside her office at Columbia's Teachers College.
The New York Police Department is investigating the matter as a hate crime. No arrests have been made and no suspects have been identified.
Nooses have long been seen in the United States as potent symbol of racist lynchings and hatred of blacks and experts speculate they may have replaced the burning cross used by the Ku Klux Klan.
It was the second involving a noose to occur this week in New York, after the arrest of an 18-year-old woman earlier this week for hanging a noose and threatening to hang the children of her black neighbors.
At least 10 copycat incidents have been reported across the United States in recent weeks following the news reports of racial tensions in Jena, Louisiana.
In the small town, three white students hung nooses from a schoolyard tree after black students sat under it.
Constantine, 44, a specialist in psychology and education, issued a statement saying, "Hanging the noose on my office door reeks of cowardice and fear on many many levels."
Outside Columbia more than 100 students gathered to protest against the incidents. The university's president, Lee Bollinger, called the act "a terrible incident of bias" and "an assault on all of us."
"Tolerance and mutual respect are among the core values of our diverse community, and all of us must confront acts of hate whenever they occur within it," Bollinger said.