A protest at the University of Mississippi against the re-election of President Barack Obama grew into a crowd of about 400 students, with racial slurs shouted as rumours of a riot spread on social media.
Two arrests were reported but university officials said there were no injuries or property damage.
A university spokesman said the gathering began after midnight with 30 to 40 students protesting against Mr Obama's re-election but it quickly grew. Rumours exploded on Twitter after student journalists posted a video calling the gathering a riot.
Chancellor Dan Jones condemned the disturbance, saying most students and faculty are "ashamed" of the actions of a few.
The university has held several events this year to mark the 50th anniversary of the enrolment of its first black student, James Meredith.