A small white plastic box was found discarded outside the entrance to the media centre, the Salle d'Exposition near to La Rascasse.
Local police initially closed off the entrance to the media centre at around 9.45pm local time, forcing journalists leaving to exit through a back door.
The area was then sealed off to allow the bomb disposal expert to check the package over before he eventually declared it suspect.
A small crowd that had gathered, including a handful of journalists and photographers, were pushed back to a distance of around 50 yards in between the motorhomes belonging to Formula One supremo Bernie Ecclestone and the FIA.
As the expert prepared to detonate, the group was asked to retreat a further 20 yards near to the entrance of the McLaren motorhome.
Finally, after 20 minutes working on the package and wiring it up, it was eventually exploded, creating a considerable noise and leaving shards of white plastic strewn across the floor.
It is the second time in successive years a bomb disposal unit has been summoned to the paddock ahead of the Monaco race.