The accident happened near the entrance ramp to eastbound M-14 at Main Street in Ann Arbor Township and stopped traffic in all directions.
Police say a man driving a semi-tractor pulling an RV was the one who caused the crash. The accident occurred just before 5 p.m. Thursday.
There were 13 cars, one RV with a trailer and one semi truck involved in the crash, according to Michigan State Police.
Two patients had been transported to the University of Michigan Hospital in unstable condition. All of those injured are expected to recover.