A woman has died several days after she was assaulted in a town centre.
The woman was taken to hospital with serious injuries following the attack in the Bridge Street area of Lampeter, Ceredigion, at 18:00 GMT on Thursday.
Two of the four men who were originally arrested in connection with the assault have been released with no further action.
A 40-year-old man remains in custody and a 27-year-old man has been released on bail.
Det Ch Insp Anthony Evans said: "This is now a murder enquiry and I am appealing to anyone with information that could help the investigation, no matter how insignificant you may feel it is, please get in touch.
"I would like to reassure the public that we are not looking for anyone else in connection with the incident."