Detectives investigating an "elaborate hoax" which saw two suspicious devices closing down parts of a city centre have released CCTV footage of three women believed to have been involved.
Two areas of Canterbury in Kent were evacuated on the evening of August 26 after a suspicious package was found near a railway line and a second suspect package was discovered after a fire started in a baby changing room in an Marks & Spencer store.
Detectives said they now know that at least three pay-as-you-go mobile phones were used in the execution of these hoaxes to allow those behind it to contact police, each other and the media.
The phones were bought in a mobile phone shop in the West End of London at around lunchtime on Sunday August 14, although they were activated for the first time on the day before the hoaxes were committed, in the south-east London area.
Police are issuing CCTV images of a group of three women who attended the shop and purchased the three phones who they believe may hold vital information. The case will also feature in the BBC's Crimewatch programme.
Detective Chief Inspector Tom Richards, of Kent Police, who is leading the investigation, said: "Following an extensive investigation, we have established that the bomb hoaxes in Canterbury on Friday August 26 appear to be a sophisticated criminal act with elaborate hoax devices guaranteed to cause considerable disruption and distress to the people and businesses in Canterbury and to the travelling public.
"This is a very unusual case and we believe those responsible are an organised group who had put serious and meticulous planning into committing these offences, although at this time the motive behind the hoaxes is still unclear and no-one had claimed responsibility for them.
"I really want to appeal to the public to help us identify the people in the CCTV images. These people could be from anywhere so I would ask people to take a good look at the images and if you recognise anyone, please call us. I would especially appeal to the women who were in the phone shop to get in touch with us as we believe they might hold information vital to this case."
Previously-released CCTV showed a man who was seen in Marks & Spencer shortly before the alarm was raised. He was white, aged 35 to 40, 5ft 9in, and was wearing dark clothing, possibly cycling clothes, including leggings and cycling shoes, and a dark baseball cap.
Anyone with information is asked to call the Kent Police incident room on 01303 289600, or Crimestoppers on 0800 555 111.