Detectives are continuing to question Constance Marten and her boyfriend Mark Gordon after the remains of a baby were discovered in Brighton.
On Wednesday night, police confirmed the remains of a baby had been found in a wooded area of the city, close to where the pair were detained.
A huge police presence remains in the area on Thursday, as investigations continue.
A crime scene is in place where the body was found and a post-mortem is being carried out.
An extensive cordon covers allotments that were at the centre of the search, as well as nearby houses, and a woodland area.
A blue forensic tent is in place in Golf Drive which leads to the allotments, while several police vans remain stationed along the road.
Orange cones have also been set out to mark the edge of the cordon.
Five uniformed officers from the Metropolitan Police were seen entering the cordoned-off allotment plots on Thursday morning.
Marten and her boyfriend Gordon – a convicted sex offender – were detained in Brighton on Monday on suspicion of child neglect after a member of the public spotted them at a shop.
They were further arrested on suspicion of gross negligence manslaughter on Tuesday after police said they had refused to say where the baby was.
The couple had been missing with the baby since 5 January when their car caught fire on the M61 near Bolton.
It is believed Marten, who comes from an aristocratic family with royal connections, gave birth to her baby one or two days before the incident, and neither she nor the child received any medical attention while the family were missing.
Police lodged an appeal for the couple to come forward, saying the baby was “at the heart of the investigation” and that concerns were rising “day by day” for the child’s wellbeing.
Marten and Gordon were spotted numerous times around the UK, including in Liverpool, Essex, south London and East Sussex.
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Before their arrest, they were last seen in Newhaven – about seven miles east of Brighton – on 8 January.
Authorities believe they were sleeping in a tent and avoided detection by using cash, hiding their faces and usually moving around at night.
