"We have to be concerned about a copycat being out there," he said, adding that police had no suspects or motives in either incident.
At Columbia, detectives were still reviewing several hours of videotape captured by a half dozen security cameras in and around the building where the noose was found Tuesday morning. It was strung over the office doorknob of Madonna Constantine, a professor of education and psychology who has written extensively about race.
In the other case, the noose was found Thursday dangling from a lamppost above some scaffolding erected around the post office, which was closed for nearly three years after the Sept. 11, 2001, terrorist attacks because of contamination from asbestos, mercury, and debris from the fallen twin towers.
"At this point, there was no target that was evident or any motive," a US Postal Inspection Service spokesman, Al Weissman, said yesterday morning. He said no postal workers had reported any threats or other problems.
Both incidents were being investigated by the New York City Police Department's hate crimes unit, which returned to the Ivy League campus Thursday after a caricature of a yarmulke-wearing man and a swastika was found on a university bathroom stall door. Police said there was no reason to believe the two campus incidents were linked.
