LONDON (AP) – A parcel bomb exploded and injured a woman at Britain’s driver and vehicle licensing agency Wednesday, the third parcel bomb to injure office workers in as many days at sites connected with cars and traffic regulations.

The Association of Chief Police Officers said seven such devices had been mailed in the past three weeks, causing minor injuries to six people. The group did not say whether they believed all the devices were part of a single campaign.

“The packages received so far have caused minor injuries, but could have been more serious,” said Assistant Chief Constable Anton Setchell, who is the national coordinator for domestic extremism.

Bomb disposal experts destroyed another suspicious package in a controlled explosion in Portsmouth, police said. “At this stage, it is not being linked to any of the postal bombs across the U.K.,” said spokeswoman Sally Evans.

She gave no details about where the suspicious package was found.

Wednesday’s explosion occurred at the Driver and Vehicle Licensing Authority in Swansea. The woman’s injuries were not believed to be life-threatening, police said.

The DVLA processes drivers’ licenses and vehicle registrations.

On Monday, a woman was injured by an exploding parcel at the head office of Capita Group PLC in London. The company has numerous government contracts, including designing and running a system for enforcing the congestion charge imposed on motorists in central London.

Two people were injured Tuesday in an explosion at Vantis PLC in Wokingham, 40 miles southwest of London. A spokesman for the accounting company said the parcel was addressed to a client whom he refused to identify.

News reports, however, said the company’s clients included Speed Check Services, which provides digital speed enforcement technology to police.

Kent police said a resident in Folkestone, 70 miles southeast of London, suffered minor injuries on Saturday when a letter exploded as it was being opened.

On Jan. 28, Kent police said a homemade device exploded at a residence in Chatham, 35 miles southeast of London, causing minor injuries to a resident. Chief Inspector Peter Wedlake said it appeared to be “a very small, crude homemade device that may have contained some firework powder.”

Authorities also disclosed Tuesday that three devices were mailed to companies in Oxfordshire and the West Midlands area in January.

It wasn’t clear which of the earlier incidents were included in the six mentioned by the Association of Chief Police Officers.