Six men have now been arrested on suspicion of murdering a missing woman from Exeter.
Lorraine Cox was last seen in Exeter city centre in the early hours of Thursday, 1 September and was reported missing two days later.
Following a “significant development in the case”, Devon and Cornwall Police arrested six men aged between 22 and 71.
Detective Chief Inspector Lee Nattrass, from the major crime investigation team, said: "Lorraine Cox had initially been treated as a missing person following concerns for her welfare from her friends and relatives.
"However, following a significant development in the case, we are now treating this as a murder investigation.
"Extensive searches by specialist officers are currently taking place in and around Mary Arches Street in Exeter city centre.
A cordon remains in place and the public are likely to see police activity ongoing in the area for the next few days.
"We would like to hear from anyone who believes they had seen or heard from Lorraine since 1 September as a matter of urgency.
"If you have any information that can assist us with our investigation, please contact the police on 999, quoting log 285 for 9 September."
Police said Ms Cox's family have been informed of the development and are being supported by trained liaison officers.