Police remain outside a home after a murder probe was launched.
A home in Southchurch Road caught alight at around 2.45am on Saturday morning.
A 66-year-old woman was rescued from the property and was rushed to hospital.
But she has since sadly died.
Essex Police is now treating the woman's death as a murder.
A 41-year-old from Southend, who was known to the victim, has been arrested on suspicion of murder.
Read more >> Murder probe launched after woman dies in Southend house fire
A spokesman from the force, said: "We have launched a murder investigation after a woman died in a fire in Southend.
"We were called by colleagues in the fire service to an incident in Southchurch Road at about 2.45am on Saturday 3 July, after a property caught fire.
"A woman was rescued from the property and was taken to hospital for treatment.
"Sadly, a 66-year-old woman has now died.
"A thorough examination of the fire site has been carried out by experts and we are now treating the woman’s death as murder.
"A 41-year-old man from Southend, who was known to the victim, has been arrested on suspicion of murder and remains in custody this morning.
"Anyone who believes they have information on the woman’s death or the hours leading up to the fire should call us on 101 and cite 42/128551/21.
"You can also submit a report online or use the 'Live Chat' button to speak to an online operator between 7am-11pm."
Information can also be given anonymously to Crimestoppers or call 0800 555 111.
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