(NBC Connecticut) -- Central Connecticut State University, a public university in New Britain, Connecticut, has issued a campus emergency alert.
They are asking everyone on campus to seek shelter, stay indoors, lock doors and close windows.
Police sources said a potentially armed man was seen entering one of the halls at CCSU.
School officials said there has not been a shooting and there is no active shooter.
State police said they have a "number of troopers" at the scene at the request of CCSU police. Tactical teams have been called to the scene.
Witnesses said police are running with long guns, telling students to take cover.
Two students said they saw a masked man walking on campus with a sword and carrying a backpack. Whether this is connected to the alert is not yet known.