Motorists were urged to avoid the Penarth Road area of Cardiff after the crash just after 3.30am
Two vehicles collided on busy road into Cardiff in the early hours of Monday morning and motorists were warned there could be delays of up to three hours on Monday morning.
The incident, involving a Royal Mail lorry and a police vehicle, happened at 3.34am on Penarth Road in Cardiff.
The Royal Mail lorry crashed into The Buzz building on Penarth Road near the junction with Corporation Road and Clare Road in Grangetown.
The scene at The Buzz after the crash
The two people in the police vehicle were taken to the University Hospital of Wales in Cardiff where they received treatment for non-life threatening injuries.
The male driver of the Royal Mail lorry was examined and sent home and is said to be "shaken" following the incident.
Police had urged drivers to avoid the area during this morning’s rush hour before reopening the road just after 9am.