Police were called at around 2am on Tuesday (29 December) over concerns for a woman with a head injury in Chapel Street, Luton.
Emergency services attended the scene and the woman in her 50s was taken to hospital, but sadly she died yesterday (Wednesday).
On Tuesday, two men in their 50s, a man in his 30s and a woman in her 50s were arrested on suspicion of causing grievous bodily harm in connection to the incident.
They were released under investigation as detectives continue their enquiries.
A post-mortem examination is due to be carried out on Saturday (2 January) to establish the cause of the woman’s death.
Detective Inspector Justine Jenkins, from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit, said: “We are carrying out a number of enquiries and have arrested four people in connection with this tragic incident.
“We understand that news such as this can be unsettling for the community and we are working hard to establish the exact circumstances around what happened.
“If anyone has any information that you feel may assist us, please do get in touch.” Anyone with any information should call 101 or use our online reporting tool quoting Operation Network.
You can also contact Crimestoppers, anonymously, on 0800 555111.