The first incident happened Sunday at the East Union Marketplace Lobby. Two more incidents happened Monday night.
The second was just after 7 p.m. at the Bostock Library and the third incident was just before midnight at the Central Campus Apartment area.
Anyone with information about cases is asked to call Duke Police at (919) 684-2444, or Durham CrimeStoppers at 683-1200. CrimeStoppers pays cash rewards from information that leads to an arrest in a felony case.