Updated: December 2, 2015 9:38 AM ET | Originally published: December 2, 2015 9:18 AM EST

The University of North Carolina at Chapel Hill went on a brief lockdown early Wednesday after police received a report of an armed and dangerous person on campus.

School officials issued an emergency alert about 9 a.m., warning students of a possibly armed individual near the ROTC Building and Venable Hall, UNC of Chapel Hill spokeswoman Jeni Cook told TIME.

“Campus police have blocked off the area around the building,” she said. “They’re advising everyone to stay inside and avoid windows.”

The threat was cleared about 30 minutes after the school activated emergency sirens, shutting down classes and campus activities, officials said.

“UNC has issued the instruction ‘All clear. Resume normal activities’ to the campus community,” an updated alert said. “The all clear signal means the threat to the campus is over.”

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