The identity of a baby girl found dead at a recycling centre four months ago remains unknown after police checked 11,000 hours of CCTV footage.
The newborn, thought to be less than 48 hours old, was found by staff at the Sackers facility in Needham Market, Suffolk, on 14 May.
She is believed to have been put into one of a possible 52 commercial bins in Ipswich and the surrounding area.
CCTV from collection sites has failed to provide fresh evidence, police said.
It is thought the girl - referred to by Suffolk Police as Baby S - could have been put in a bin and taken to the site between 13 and 14 May.
A post-mortem examination on 19 May was inconclusive and the results of further pathology tests are still pending.
Police spent three weeks searching the Sackers facility looking for any identifying items such as baby blankets, toys or paperwork.
While some items were taken away, officers said these "have not assisted in identifying the parents to Baby S".
They also visited 800 properties in the areas of the relevant bin collections and have completed an initial review of the CCTV footage spanning the period from midnight on 12 May through to the time when the bin was collected at each location on 14 May.
"Unfortunately, we cannot specify the location where this little baby girl was left prior to being conveyed to Sackers," Det Insp Karl Nightingale said.
"We are still trying to establish if Baby S died before being left at one of the collection sites and examinations in relation to this remain ongoing with support from medical experts.
"It is anticipated these will still take many weeks."
Officers have renewed their appeal for the mother, or anyone who might have information, to come forward.