Police have released a new appeal for information relating to three babies abandoned by the same parents shortly after birth in east London.
A reward of £20,000 is also being offered by Crimestoppers.
It is exactly one year since Baby Elsa was found alive in a shopping bag near the Greenway footpath in east London, just an hour old.
Police have now released a photo of the Boots carrier bag.
The baby was extremely cold so hospital staff named her "Elsa" after the character in the Disney film Frozen.
Baby "Harry" was found in September 2017, wrapped in a blanket, again shortly after he was born.
The other newborn baby "Roman" was found in freezing temperatures in February 2019, wrapped in a white towel and placed in a shopping bag.
As the BBC revealed last year, DNA tests presented to East London Family Court established that all three abandoned babies are full siblings.
All their names have been changed and all three are in good health.
Police have reviewed more than 450 hours of CCTV footage and completed a full DNA profile of the children's mother.
Specialists working with the police believe the mother and possibly father have been living in Plaistow or East Ham for the last six years.
Detective Inspector Jamie Humm said: "We have serious concerns for the wellbeing of the parents, especially the mother."
He said he believed someone in the area will have been aware of the mother's pregnancies and "within the community there may have been concerns for this mother's welfare".
He urged people to contact the police if they had any information, no matter how small it may seem.
He said the three children were "thankfully" healthy.
The Family Court heard in December that Elsa was still in foster care and "doing very well".
The older children have been adopted, and that is Newham Children's Services' plan for Elsa too.
However, the local authority cannot register Elsa's birth while the police investigation is active.
Without that, the local authority cannot complete its evidence before the family court and seek its approval for her adoption.
The court heard that officials were "very concerned" about the delay.
'State of uncertainty'
There have been nine hearings so far before the senior judge in East London Family Court, Carol Atkinson.
She said in December that Baby Elsa was living with an "ongoing state of uncertainty", and it was not possible for carers to "progress the relationship" with her older siblings while the proceedings were still going on.
Professor Lorraine Sherr of University College London has made a study of children abandoned at birth.
She said the delay in the court process was a "double whammy" for the little girl.
"She can't get on with her new life, or build relationships with her siblings," she said. "Nor does she know who her parents are."
She said children who are abandoned at birth can spend many decades searching for their parents, even well into their 70s and 80s.
