Sgt. Roy Hoskins with the St. Joseph Police Department said a 19-year-old driver was driving too fast on Highland Ave., went around a curve, and slammed into the side of a postal building.
Police believe alcohol or drugs played a role in the crash.
Part of the southwest corner of the building collapsed after the impact.
A building inspector monitored the building to make sure it was structurally safe.
The people injured in the crash do not have life threatening injuries.
No tickets have been issued and charges are pending in the case.