Police received numerous calls reporting the sound of gunshots at about 12:40 a.m., police spokeswoman Margo Rohrbacher said. Officers went to the campus but did not find anything suspicious, she said.
However, a few hours later, campus security officers spotted shell casings on the ground in an area of the campus on Olive Avenue near Palm Avenue, Rohrbacher said.
Police have spent the day working with campus security to search the campus, but have not recovered any weapons, she said. Police are also using dogs that are trained to detect gunpowder.
Classes remain on a normal schedule, and Rohrbacher said, "it's a regular day in campus life."
The university has asked students report anything suspicious, she said.