43-year-old ex-EastEnders actress Sian Blake and her two young sons aged four and eight, were reported missing on December 13.
Blake’s partner Arthur Simpson-Kent, 48, initially alerted police but has since gone missing himself.
After searching Blake’s home in south-east London, three bodies have been discovered in the garden.
“As yet, we have not formally identified the bodies but this is a significant development and Sian’s family have been informed,” said Met Police Detective Superintendent Paul Monk.
The case is being treated as a murder investigation.
Sian Blake played Frankie Pierre in the British soap EastEnders from 1996-97. After fulfilling subsequent roles, Blake retired from acting once she developed motor neurone disease.