A noose discovered hanging on the office door of a black professor at Columbia University in New York triggered outrage yesterday at the latest in a disturbing series of copycat racist incidents across the US.

A colleague of Madonna Constantine, 44, who has written several books on racism, discovered the noose - a reviled reminder of lynchings in the Old South - at 9.40am on Tuesday.

Detectives at the New York hate crime task force were on campus last night as hundreds of students prepared to march in an antiracism rally.

At least a dozen similar incidents have occurred in the US since a nationally televised controversy last month in Jena, Louisiana, where three white students hung nooses from an oak tree outside the town’s high school.

The three students were sent home but not prosecuted. Racial tensions intensified after a white student was beaten unconscious. Six black students - who became known as the “Jena Six” - were initially charged with attempted murder. Their case became a national cause célèbre for the modern civil rights movement and was the impetus for a huge protest march in Jena on September 20.

There is little evidence that a new wave of racism is on the rise in the US. The Jena episode appears, however, to have reintroduced the noose as the favoured symbol of people seeking to stir up racial tensions in a country where the legacies of segregation and slavery still exert enormous influence.

The reaction at Columbia University’s Teachers College was of shock. On a campus considered a bastion of liberal activism, the incident was all the more disturbing because it followed several other racist episodes in recent months, including graffiti on a bathroom wall and the arrest of two students last year for drawing swastikas in a hallway.

“This is an assault on African-Americans and therefore it is an assault on every one of us,” said Lee Bollinger, the university president. “I know I speak on behalf of every member of our communities in condemning this horrible action.” Joe Levine, a Columbia spokesman, said that the university’s leadership was appalled by the incident. He said that there had been a spate of “bias-related” incidents in recent years, “but I’ve never seen anything like this here”.

Addressing an antiracism rally at campus yesterday, Dr Constantine described the noose hanging as a “heinous and hugely upsetting incident”. She added to cheers: “Hanging a noose on my door reeks of cowardice and fear on many, many levels. I would like the perpetrator to know that I will not be silenced.”

The controversy follows another racially charged episode at Columbia last month: a speech on campus by Mahmoud Ahmadinejad, the President of Iran, which stirred up anti-Semitic, anti-Islamic and homophobic tensions.

University authorities said that there were closed-circuit television cameras on the entrance to the building where the noose was left but not in Dr Constantine’s corridor. Only those with a Teachers College identity card or proof that they are affiliated to the college can get into the building.

Police said that they were investigating whether the incident stemmed from tension between Dr Constantine and a rival professor. Dr Constantine told police that the other professor had replaced her while she was on extended leave and was upset when she returned to reclaim her position.

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