Footage of a man seen running away from a house where a heavily pregnant woman was stabbed to death in south London has been released by police.
The CCTV shows a figure walking towards Kelly Mary Fauvrelle’s Croydon home at about 03:15 BST on Saturday, then running away 10 minutes later.
Ms Fauvrelle, 26, died at the scene but her baby was delivered by paramedics and he remains in a critical condition.
The Met said it was an “extremely challenging investigation”.
Det Ch Insp Mick Norman said officers “need to identify the man shown in the footage urgently, even if only to eliminate him from our inquiries”.
Police had been called to the address in Raymead Avenue, Thornton Heath, over reports of a woman in cardiac arrest.
Paramedics tried to save the 26-year-old, who was eight months pregnant, but she died at the scene.
Her baby boy has been named Riley by her family and he remains in hospital.
Det Ch Insp Norman said he was aware of “speculation about whether Kelly’s attacker was known to her” but said police “are not in a position to say and we must retain an open mind”.
Two men have been arrested on suspicion of murder.
A 37-year-old man has been released with no further action while a 29-year-old man was bailed until a date in August.