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.
Three men were initially arrested on suspicion of conspiracy to murder.
Officers have since arrested another person, a 30-year-old woman from Southampton on suspicion of conspiracy to murder.
She has been released under investigation while officers continue with their enquiries.
The 63-year-old man and 50-year-old man have also been released under investigation.
The 29-year-old man has been 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 police with this investigation, please contact police by calling 101 and quoting Operation Blackboard or 44200068330.
Alternatively, people can call Crimestoppers anonymously on 0800 555 111.