Police were called at Lincoln College on Friday afternoon after reports that a girl was seen brandishing what appeared to be a weapon.
Dozens of Lincolnshire Police officers attended the scene in a swift firearms response from the force.
Many students at the institution were evacuated from the building and were standing outside Lincoln College.
Lincolnshire Police spokesman James Newall told The Lincolnite the situation is now under control and that the girl is assisting officers with their investigation.
The girl, who is a Performing Arts student at Lincoln College, was reportedly carrying a prop gun.
More photos from the scene on our Facebook page.