An investigation has been launched into Scotland Yard's handling of the Sian Blake case.
The Independent Police Complaints Commission will examine the response to concerns for the welfare of the former EastEnders actress and her two young sons Zachary and Amon, as well as the subsequent missing persons inquiry.
It is understood concerns about domestic violence were raised by a relative of Ms Blake to the NSPCC on December 16.
A missing person's investigation started on the same day after police attended the family home in Erith, Kent.
On Tuesday - almost three weeks later - three bodies were discovered in the garden of the property, triggering a murder inquiry.
Arthur Simpson-Kent, Ms Blake's former partner, is being sought by police. He is believed to have fled to Ghana.
Confirming that an investigation is under way, the IPCC said police began their enquiries following a "report of concern" by visiting the home where officers spoke to Simpson-Kent.
"Sadly, the bodies of Sian and her two children were found at the Pembroke Road address 20 days later, on 5 January 2016," the watchdog said.
"The Independent Police Complaints Commission (IPCC) investigation will examine the police response, actions and decision-making following the reported concern for welfare."
ITV News obtained photographs of Simpson-Kent, 48, at Kotoka Airport in the Ghanaian capital Accra - three days after he was quizzed by police over the family's disappearance
Yesterday Ms Blake's sister Ava said he will have to "answer to God" for his alleged actions, revealing that her sibling had told their mother, Pansy, that she wanted to get out of her relationship "a long time ago".
Ms Blake, 43, had motor neurone disease - a fatal, rapidly progressing illness which affects the brain and spinal cord - and was reportedly looking "very frail" before she vanished.
She was last seen with her sons in Waltham Forest, east London, on December 13.
Post-mortem examinations indicated that the three died as a result of head and neck injuries.
IPCC Associate Commissioner Tom Milsom said: "The loss of Sian and her two young boys Zachary and Amon, is a tragedy and my thoughts are with their family during this very difficult time.
"The IPCC will be conducting a thorough investigation into how police responded to the concerns for their welfare and their disappearance."