Jo Sheen was reported missing by her family on 22 February this year after they had not heard from her for several months.
The last known corroborated sighting we have of Jo is on Thursday 5 December 2019 when she travelled from Fareham, back to Southampton, with a friend.
Joanne is still missing and her body has not been recovered.
Four people were initially arrested on suspicion of conspiracy to murder.
Officers have now arrested a fifth person, a 53-year-old man from Southampton, on suspicion of conspiracy to murder. He remains in police custody at this time.
The 63-year-old man, 50-year-old man and 30-year-old woman were released under investigation.
The 29-year-old man was bailed with conditions.
Enquiries are ongoing.
Police continue to appeal for information in relation to this case.
If anyone has any information that may assist this investigation, contact police by calling 101 and quoting Operation Blackboard or 44200068330.
Alternatively people can call Crimestoppers anonymously on 0800 555 111.