Four people were taken to hospital after a letter bomb exploded at the main DVLA centre in Swansea on Wednesday. It was the third such attack on motor-related targets in three days.
Staff were forced out of their offices after the attack on the DVLA centre. A total of seven devices have been received at locations in England and Wales in the past three weeks.
Army bomb disposal experts were called to the Driver and Vehicle Licensing Agency building in Swansea after the device exploded. Four staff had to be taken to hospital.
Police officers make their way into the DVLA's headquarters in Swansea. The letter bomb explosion took place just after 0900 GMT.
Office workers in Swansea looked down on the drama unfolding below. The blast has been linked to explosions in Wokingham, London and Folkestone.
On Tuesday, a bomb exploded in Wokingham, Berks, at a firm linked to speed camera company Speed Check Services. Police forensic officers went to the scene.
Army bomb disposal experts from the Royal Logistics Corps attended the scene of the Wokingham letter bomb. Two men were slightly injured in the blast at accountants Vantis.
On Monday, there was a letter bomb explosion at the offices of London congestion charge operator Capita. Police sniffer dogs were brought in.
Armed police officers stood guard at the Capita offices in Victoria, central London. One female worker suffered minor hand injuries in the blast.