A murder investigation is under way after a 48-year-old woman died and a further eight people were taken to hospital following a fire at a property in Hounslow early on Wednesday, the Metropolitan Police said.
Officers were called to a property on Berkeley Avenue at just after 1am following reports of a fire.
A woman died in hospital, while another woman, 40, remains in a life-threatening condition.
The force said six men and one woman who were taken to hospital have since been discharged with minor injuries.
Police said a murder inquiry is now under way, but no arrests have been made.
Detective chief inspector Neil John, who is leading the investigation, said: “Our thoughts are first and foremost with the victim’s family and loved ones at this extremely difficult time, as well as everyone who has been injured.
“Our enquiries are progressing at pace as we work to establish the full circumstances surrounding the fire, which we believe may have been started deliberately.
“We understand this to be an isolated incident within a residential address; however, we understand it will cause concern within the local community.”
Read MoreHow Salmonella from eggs can cause deadly infections amid UK outbreak
