Detectives are treating the death of a 20-month-old girl as murder and have named her mother as a suspect.
Angela Whitworth, 40, is believed to have fled to Kenya the evening before the body of Sarah Dahane was discovered by police in Bicester, Oxfordshire, on May 16.
Detective Chief Inspector Ian Hunter, of Thames Valley Police, said: "We are investigating this incident as murder.
"However, I am keeping an open mind as at this time I cannot exclude an accident or natural causes contributing to Sarah's death.
"Sarah Dahane was a healthy, thriving and well-nourished child who was found dead with no obvious signs of trauma.
"This is a detailed and thorough investigation to establish the death and identify the exact circumstances into how and why Sarah died.
"There were ongoing legal proceedings regarding custody of Sarah between her mother and father. Angela Whitworth is 40 years old. She is a suspect but at this stage is believed to be in Kenya."
Mr Hunter continued: "Until we are in a position to establish the cause of death we are of course keeping an open mind into what happened and we are working with law enforcement agencies, including the Foreign and Commonwealth Office and Interpol, and the Crown Prosecution Service to further the investigation.
"Police responded to a call from Sarah's father, Nabil Dahane, expecting contact as Sarah had not been presented at an agreed meeting point on Thursday morning."
The body of the baby was discovered by police at a property in Herald Way, Glory Farm, Bicester, having forced entry. Mr Hunter said that the post-mortem examination was inconclusive with no visible signs of injury and further tests were being carried out.