Campus police were trying to determine whether the action constituted a hate crime, school president Royce Money said Monday. No threat was left with the noose.
Blacks make up as much as 13 percent of a student body that numbers about 4,700.
"I'm more angered than I am anything else," Money told The Associated Press on Monday. "Someone has jeopardized the fine reputation of a top quality academic institution and because of the action of one person, the entire image of a university is challenged."
ACU Police Chief Jimmy Ellison did not immediately return a phone call Monday. The Abilene Reporter-News said in its online edition Monday that police are unsure whether only one person is responsible.
Investigators with the campus police have consulted with Abilene police and the FBI, school spokeswoman Lynn Bruton said, adding that active participation from either or both is "certainly not out of the realm of possibility."
The office is in the school's student union, which is the most heavily trafficked building on campus, Money said.
"It's open all the time," Money said of Watkins' office. "That adds to the difficulty of the investigation."
Nooses are emblematic of racial tension in American history, evoking images of an era when blacks were lynched in this country.
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