Someone painted a threatening message about president-elect Barack Obama in a tunnel at North Carolina State University where students are encouraged to speak their minds, police said Wednesday.

University police Capt. Jon Barnwell would not provide details about a comment painted in what is known as the Free Expression Tunnel, but at least one student said it suggested Obama be shot and referred to him with a racial slur.

Campus authorities were notified of the comments after classes began Wednesday.

"Some Obama supporters had gone in and written some pro-Obama stuff last night," Barnwell said. "Sometime between then and this morning, someone else went in there and doctored it up with some statements that could be borderline threats."

The tunnel was built in 1939, and donated to free speech in the1960s. The university painted over all the tunnel's messages Wednesday because officials felt the disparaging comments were "going over the edge of what was acceptable," Barnwell said.

Biological science student Marlena Taylor said she walked past the tunnel while heading to class just after 10 a.m. Wednesday. She said the message was written in red letters against a black backdrop and said: "Let's shoot that N----- in the head." Nearby, others had written pro-Obama sentiments.

"I was stoked when he won. When I saw (the graffiti), I was pissed because I don't like ignorance," said Taylor, 22, who is biracial, like Obama. "It's the Free Expression Tunnel, but some opinions need to be kept to yourself. You need to take into account that you're offending people."

Barnwell said investigators are still working to determine who wrote the comments in the tunnel. Anyone with information is asked to contact campus police.