Police are hunting for the children's father, Arthur Simpson-Kent, and are investigating reports he may have fled to Ghana
Former Eastenders actress Sian Blake and her two sons died as a result of head and neck injuries, Scotland Yard says.
Police are treating the deaths as murder after the bodies were found in the garden of the family home in Erith, Kent, on Tuesday.
A post-mortem examination confirmed the identities of the victims - Blake and eight-year-old Zachary and four-year-old Amon.
Further tests are to be carried out in the coming weeks.
Police are hunting for the children's father, Arthur Simpson-Kent, and are investigating reports he may have fled to Ghana.
"Significant attempts" had been made to hide the bodies - which were found when police dug up the garden after sniffer dogs "indicated areas of interest".
Sian Blake and her children were last seen in east London on 13 December, with her car found in the Bethnal Green area on 3 January.
Her sister has revealed she was planning to leave Arthur Simpson-Kent over the Christmas period.
"She had asked to come back home and we said yes, so we really tried to plan on getting her to move back home," said Ava Blake.
"She said she would come back, sort of Christmas week, and after Christmas they would arrange about selling the property she lived in.
"She didn't want to throw (Arthur) out on the street but give him time to find somewhere else to live. That was the only point she was wavering on."