CHICAGO (CBS) — Six DePaul University students were robbed in a span of about 30 minutes overnight, part of a string of robberies by the same group of suspects driving around in a white Audi SUV.

Chicago police said all the same group of four or five suspects committed four robberies between midnight and 12:40 a.m. Thursday morning.

Sometime between 12:15 a.m. and 12:25 a.m., a 20-year-old man was walking on the 2300 block of North Sheffield Avenue on the DePaul Campus, when a white Audi SUV pulled up with four young men inside. Two of them got out, and demanded his belongings, according to Chicago Police and DePaul Public Safety officials.

Chicago police said the suspects were wearing surgical masks. They did not show a gun, but implied they were armed.

Between midnight and 12:35 a.m., Chicago police said another 20-year-old man was walking near the Clybourn Metra station, at Ashland and Armitage, when two young men got out of a white Audi SUV, and stole his belongings at gunpoint. At least one suspect was wearing a surgical mask.

Around 12:25 a.m., a group of four DePaul students – three men, ages 18 and 19, and an 18-year-old woman – were walking near Sheffield and Altgeld, about a block north of campus, when a white Audi SUV pulled up, and three suspects wearing medical masks robbed them at gunpoint.

DePaul Public Safety officials issued a campus alert about those three robberies. All six victims were DePaul University students.

“In the aftermath of this concerning sequence of incidents — a robbery and two armed robberies — DePaul’s Public Safety continues with the Chicago Police Department 18th District and Area Central Detective Division to make our neighborhood safer. We remind students, faculty and staff to report any suspicious activity to Chicago Police by calling 911, or to call DePaul Public Safety at 773-325-7777,” DePaul Public Safety director Bob Wachowski said in a statement.

Chicago police said the same robbers involved in those attacks also were responsible for a robbery in the 900 block of South Western Avenue around 12:40 a.m., more than four miles away from the other three holdups. The suspects in that robbery also were wearing surgical masks and driving a white Audi SUV.

No one was in custody Thursday afternoon. Area North detectives were investigating.