The 43-year, who played Frankie Pierre in the hit soap, went missing from Erith, Kent, with her children Zachary, eight, and Amon, four.
Officers are also concerned for the welfare of Miss Blake's partner and the children's father, Arthur Simpson-Kent, 48.
He has not been seen since December 16 when officers spoke to him at the family home in Erith.
Mr Simpson-Kent was subsequently reported as a high-risk missing person, and officers have been unable to contact him since that date.
Miss Blake, who suffers from a serious, life-threatening condition, was last seen on Sunday December 13 around Waltham Forest, east London, and police in Bexley, south-east London, believe she is still in the area.
Miss Blake's silver-beige Renault Scenic was found in east London, on January 3, but it is not known who parked it there.
Scotland Yard said the investigation continues to be a high-risk missing persons inquiry, but due to concerns for their welfare, the Homicide and Major Crime Command (HMCC) is now leading and is looking into whether the family may have been victims of a crime.

