The University of North Carolina at Chapel Hill has sent an emergency alert that an armed and dangerous person may be on or near campus.

Officials say the school activated its emergency sirens Sunday. Authorities also locked the doors to Carmichael Arena, site of an NCAA women's tournament game between the Tar Heels and the University of Tennessee at Martin.

Students and others on campus were advised to close their windows and doors and stay inside until further notice.

The school says the sirens are activated when there's an emergency or safety threat to the campus.