Sian Blake
Sian Blake has been missing since 13 December 2015Met Police

The hunt for former EastEnders actress Sian Blake is now being led by murder detectives after her partner, Arthur Simpson-Kent, also disappeared. The 43-year-old Blake, who suffers from a life-threatening motor neurone condition, was last seen on 13 December, when she visited family in the Leyton area of northeast London with her two sons Zachary Bilal Kent-Blake, 8, and Amon Ben George Kent-Blake, 4.

The investigation is now being led by the Met Police's Homicide and Major Crime Command (HMCC). The actress's partner has not been seen since 16 December after officers spoke to him at the family home in Erith, Kent. It was after that meeting that police first started their search for Blake and the children. The force said it was treating the disappearances as a "high-risk missing persons inquiry" and that it did not know if the family were missing together or not.

Officers are also investigating why Blake's silver/beige Renault Scenic – registration number SM54 FUO – was found in Calvert Avenue, Bethnal Green, east London on 3 January. It is not known why the vehicle was parked there and by whom.

Detective Chief Inspector Graeme Gwyn has said he is "increasingly concerned" for the family's welfare. "A number of enquiries are under way to find Sian Blake, Arthur Simpson-Kent and their two children," Gwyn said. "They have all been missing for a considerable period of time now, and I am growing increasingly concerned for their welfare. In particular, Sian suffers from a serious, life-threatening condition and we do not know if she is receiving the medication and treatment she requires to keep well.

"I am appealing directly to Sian and Arthur to get in touch with the police and let us know they are all well. I am also appealing to anyone who has seen the family or knows where they may be to get in touch as soon as possible."

Police are asking anyone with information to contact them on 020 8721 4805 or Crimestoppers on 0800 555 111.

Sian Blake is described as a black woman, 5ft 2ins tall of slim build with short black hair, who often wears glasses.

Arthur Simpson-Kent is described as a light-skinned black man who is 6ft 2ins tall. Zachary and Amon are both described as light-skinned black boys. It is not known what any of the family were wearing when they went missing.