A 36-year-old woman has been arrested on suspicion of concealing a birth after the partial remains of a newborn baby were found on a popular common.
The legs of an infant were discovered at a council depot on Tooting Bec Common in south London on September 10.
Experts found that the baby, who was white, had been born around two weeks beforehand and had gone to full term. They could not say whether the child was stillborn.
Detectives arrested the woman on Monday after members of the public said she had been at the end of her pregnancy at that time.
She has been detained for four weeks under the Mental Health Act, Scotland Yard said.
Detective Chief Inspector Mark Dunne said: "She is somebody who we believe may have given birth and at this stage we can't locate that baby, so we needed to ask her about her baby."
DNA tests are currently being carried out to see if the woman is any relation to the child whose remains were found.
Detectives had contacted schools and medical centres to try to trace the infant's parents, and scoured the common for clues.
At the time, Mr Dunne said: "The focus right now is to identify the parents, particularly the mother because she or they are almost certainly going to be in need of some of the care services support."
He said today that the investigation is continuing.