The University of North Carolina at Chapel Hill was under a shelter-in-place order on Monday afternoon after the school warned that an “armed, dangerous person” was on campus.

The university sent an alert just after 1 p.m. that advised people in the area to go inside and stay away from windows. Nearly an hour and a half later, the university said in another alert that the shelter-in-place order remained in effect and said there was a “suspect at large.”

“We will provide updates as they become available,” the school said in a post on X, the social media platform formerly known as Twitter.

Students returned to class on Aug. 21 after summer break.

The university did not immediately respond to requests for comment. It was not clear whether there were injuries.

Gov. Roy Cooper of North Carolina said in a statement on social media that he had spoken with the Orange County sheriff and the state’s secretary of public safety and had “pledged all state resources needed to capture the shooter and protect the U.N.C. campus.”

Mr. Cooper said his office was in contact with law enforcement officials who were “taking precautions to protect campus safety following today’s shooting.”

“This is a tragic way to start a new semester and the state will provide any assistance necessary to support the U.N.C. community,” the governor said.

ABC 11, a local news channel, showed more than a dozen emergency response vehicles parked on campus.

A local school district, Chapel Hill-Carrboro City Schools, said that classroom instruction could continue as normal but that schools were in “secure mode,” meaning all school building doors were closed and locked and people were not allowed to enter or leave school buildings.