Troopers were called to the area of Interstate 94 and West 31st Street around 3:45 a.m. after receiving information about a three-vehicle crash, one of which was a Chicago Police Department squad car, Trooper Jayme Bufford said in an email. According to preliminary information, a vehicle coming up behind the squad car rear-ended it, leaving the driver of the first vehicle and two police officers in the squad car suffering from injuries not considered life-threatening.