Four men have been arrested on suspicion of murder after a woman was reported missing last week in Exeter.
Lorraine Cox, 32, from Exeter, Devon, was last seen in the early hours of 1 September in the city centre.
Police said they had been treating Ms Cox as a missing person but have now launched a murder inquiry following a "significant development".
The suspects aged 22, 30, 33 and 71 all remain in custody, Devon and Cornwall Police said.
Ms Cox's next of kin have been informed.
Extensive searches are being carried out by specialist officers in and around Mary Arches Street where a cordon remains in place, the force added.
"We would like to hear from anyone who believes they had seen or heard from Lorraine since 1 September as a matter of urgency," Det Ch Insp Lee Nattrass said.
Anyone with information is urged to get in touch with police quoting log 285 for 9 September.