Hundreds of students and faculty members at Columbia University in New York City rallied Wednesday afternoon to protest the hanging of a noose on the office door of a popular African-American professor.

Carrying signs reading, “Down with Racism,” the multiracial group of students, faculty and administrators rallied a day after another faculty member discovered the noose left on the office door of Dr. Madonna Constantine, 44, a professor of psychology and education at Columbia’s Teachers College.

It’s unclear who placed the noose — long associated with lynching and a symbol of racial hatred — on Constantine’s door, and New York police are investigating several scenarios, including the possibility that it was left by another professor who Constantine apparently did not get along with. The hate crimes unit of the police department would not elaborate on any other details.

Constantine, co-author of the book “Addressing Racism: Facilitating Cultural Competence in Mental Health and Educational Settings,” is considered an expert on race relations.

“This is simply unacceptable,” said Matt Johnson, 24, a student at Columbia who attended the rally. “Racism does not have a place on this campus.”

Surrounded by community activists, political leaders and her fellow colleagues, Constantine emerged at the rally to denounce the incident and to thank the college community for their support. She urged them to remain vigilant.

“I would like the perpetuator of this heinous and upsetting incident to know that I will not be silenced,” Constantine said. “I’m upset that our community was exposed to such an unbelievably blatant act of racism. Hanging a noose from my door reeks of cowardice on many, many levels.”

Students and faculty at the Ivy League university praised the administration’s quick response in alerting the college about the incident.

“This is an assault on African-Americans, and, therefore, it is an assault on every one of us,” said Lee C. Bollinger, president of Columbia. “I know I speak on behalf of every member of our community in condemning this horrible action.”