Specialist teams are scouring parkland around a mile from where aristocrat Constance Marten and her partner Mark Gordon were arrested as the desperate search for their missing baby continues.
Dozens of officers from the Metropolitan Police and a team from London Search and Rescue were seen in Wild Park Local Nature Reserve, which backs onto Hollingbury Golf Course, in Brighton, East Sussex.
The officers, some wearing jackets indicating they were dog handlers, searched underneath sticks and logs close to where the two sites meet.
A uniformed officer was seen standing guard at the entrance to the park, with dog walkers saying they saw police tape cordoning off parts of the woodland.
By midday members of the team had been on shift for 14 hours, and had walked 13km.
Marten, 39, and Gordon, 45, were arrested in nearby Stanmer Villas on Monday night, within minutes of a tip-off from a member of the public.
CCTV footage from just before they were caught appears to show Gordon, who served 20 years in US jail for rape and battery, limping and using a large stick to walk.
A heavy police presence remained in the area on Wednesday, and a red search-dog van was seen making its way into the adjoining Golf Drive, which leads to the allotments that have been a focus of the police search since the couple were arrested.
A number of marked police vehicles were stationed along Golf Drive and a uniformed officer stood guard at the bottom of the road.
Allotment users have been told that officers have forced entry to every shed on the site, and will remain there for some time.
Search teams are scouring a vast area of 7 miles by 13 miles as they try to find the two-month-old.
Marten and Gordon have been missing since January 5 when their burning car was found abandoned on the edge of the M61 in Bolton.
They avoided police for 53 days by paying for everything in cash, hiding their faces while on CCTV and moving around frequently, often at night.
It is believed Marten gave birth to her baby in the car, and neither she nor the child received any medical attention while the family were missing.
The couple have been arrested on suspicion of child neglect and gross negligence manslaughter as fears for the baby’s safety rise.
In an update on Tuesday, Detective Superintendent Lewis Basford said police still hoped to find the child safe and well, with a helicopter, sniffer dogs, thermal imaging cameras and drones being used in the search.
However, confirming Marten and Gordon had been arrested on suspicion of gross negligence manslaughter, Mr Basford said police had to consider the possibility the baby had “come to harm”.
He said officers had received no information about the welfare or location of the child since the pair were detained.
Mr Basford said: “We have had a significant period of time in the custody facility with both Constance and Mark.
“At this time we have not furthered that information, which has now obviously led to the position where we feel that the risk is getting so great that we now have to consider the possibility that the baby has come to harm.
“I can now confirm that they have been further arrested on suspicion of gross negligence manslaughter and that they remain in custody at police stations in Sussex.
“The baby was not with them and we have not found the baby as yet.”
Anyone who may be able to assist in the search for the baby is urged to contact 999.
During the search for the family both Marten’s parents, from whom she was estranged, made public appeals for her to hand herself in.
On Tuesday her father Napier Marten expressed his immense relief that she had been found, but said he remained alarmed that the baby was missing.
