Champaign police say they are investigating a string of assaults on the University of Illinois campus that left four people injured.

Police say the victims in all four attacks reported being assaulted between 3 a.m. and 4 a.m. Saturday as they walked on campus.

In each case, a group of six to seven men described as being in their mid-20s punched and kicked the victims. In a fifth incident a person reported that they were able to run away from a group of men in a blue vehicle yelling at him.

Police say three of the victims sought medical help for facial injuries.

Investigators don't know why the people were attacked but are warning people on campus to avoid walking alone in the dark.