All three were closed to traffic at around 4.45pm this afternoon to carry out the explosion.
The discovery of explosive materials at the bridge construction site were made earlier today, and although they posed no direct danger to the public, the decision was taken to dispose of the materials with the assistance of the Explosive Ordinance Disposal Unit (EOD) and to close the road as a precaution.
An announcement that the bridges would close from 4pm to 6pm was quickly updated to say the controlled explosion would take place after 6pm.
However, this was again updated to say the road and rail bridge would close from 4.45pm to 6pm to carry out the explosion earlier due to dim light and weather conditions.
The controlled explosion has now taken place and the road has re-opened to traffic.