East Carolina University cops shut down 20 parties just days into the new semester amid fears gatherings will lead to an uptick in coronavirus infections.
Officers said one of the parties was crammed with around 400 students.
This year's cohort of 5,500 students began arriving at halls on August 5, as a spate of unauthorised welcome celebrations took place over the opening weekend.
The parties violate the state ban on large gatherings of more than 10 people, enforced in a bid to curb the spread of the virus.
According to the University's website there were 28 new diagnoses among students in the week to August 8 and two among staff
Most of the celebrations were 'manageable' in size of between 25 and 50 people in attendance, Lt Chris Sutton told McClatchy News.
But around 400 students attended one of the gatherings, which was held several blocks away from the university in an area predominantly filled by off-campus housing, The Virginian Pilot reported.
Sutton said the party was mainly attended by college age revelers who dispersed when authorities arrived.
Students found to be throwing a party with more than 25 people will be given a warning first, but further violations could mean school-related consequences or even state charges.
'We've really had to change policing methods over the last several weeks due to different events across our country and now we're having to wrestle with a pandemic since our students have returned to campus,' he added.
The university allowed students to return this summer, and although classes began on Monday, students are not required to undergo virus testing before returning to campus.
According to the University's website there were 28 new diagnoses among students in the week to August 8 and two among staff.
That was up from 11 diagnoses the week before - eight among students and three among staff.
At the time the document was released the University said: 'For us to return, we must accept less independence, more guidelines and rules, and several key community expectations.
'We must work together. We hope you will accept this important responsibility for our community and our university.'
Across North Carolina there have been around 141,000 confirmed coronavirus infections and 2,313 deaths.