The road was closed at around 10.30pm with emergency services rushing to the scene. Buses were also diverted away from the area.
A large police cordon was also set up stretching from South Bridge to Leith Street.
A police spokeswoman could not give any further details at the time other than officers were dealing with an 'ongoing incident'.
It’s understood the road reopened at around 2.30am on Thursday.
We’ll bring you more details on this story as we get it.