Last week, police officers executed warrants at three addresses in Oxford as part of the investigation, which also involved conspiracy to convey articles into prison. READ MORE: Utility faces £60k fee over 'unauthorised' Oxford slip road closureThree men, aged 43, 21 and 19, and a 43-year-old woman, all from Oxford, were arrested at the time. Since then, officers from Durham Constabulary arrested a 31-year-old woman from Darlington in connection with this investigation. "Thank you to local residents for their patience while officers carried out this activity and the subsequent searches. "Anyone with information that may assist our investigation can contact us via 101 or our online reporting form, quoting reference 43260136427."