Police are concerned that a baby at the center of a massive search operation is in danger of being seriously harmed.
Hundreds of officers are combing the woods in Brighton with sniffer dogs, drones, and thermal cameras.
Constance Marten and Mark Gordon, who were arrested on suspicion of gross negligence manslaughter, have asked for more time to be questioned by police.
They were reported missing after their car was discovered ablaze near Bolton, sparking a 53-day search.
Ms Marten had recently given birth, and police believe the baby was born in the back of the vehicle, without a midwife or medical attention.
Ms Marten, 35, and Gordon, a convicted rapist and registered sex offender, were apprehended on Monday after a member of the public spotted them in a shop and reported them to police.
The couple is still being held by police, but they have not provided any additional information about the child’s condition or whereabouts.
The baby’s gender is unknown to police.
They were initially arrested on suspicion of child neglect, but were later re-arrested on suspicion of gross negligence manslaughter on Tuesday.
Speaking at a press conference on Wednesday afternoon, Det Supt Lewis Basford from the Metropolitan Police said a huge search had continued throughout the night.
The public has been asked to “remain vigilant” and report any unusual activity or “suspicious items” seen in recent weeks.
Inquiries are also being conducted in the South Downs and Newhaven, where the couple was last seen with their baby on January 8, the day before their arrest.
They were previously seen carrying a blue tent and were believed to be sleeping rough outside.
Earlier on Wednesday, teams were seen working in Moulsecoomb Wild Park, about a mile from Stanmer Villas in Brighton, where the couple was arrested.