UPDATE: PHOTOS: Police Continue To Search For Missing Baby In Newhaven

Two hundred officers from Sussex and The Metropolitan Police have worked through the night to try to locate the baby belonging to couple Constance Marten and Mark Gordon.

They were arrested after having visited a shop in Hollingbury Place, Brighton on Monday (Feb 27) and further arrested yesterday (Feb 28) with gross negligence manslaughter. They remain in custody in Sussex.

Police have been using a helicopter, sniffer dogs, drones and a thermal imaging camera to search a 91-square-mile area between Brighton and Newhaven, where the couple was last seen, and in the north of Brighton where they were arrested.

Police are urging residents in the area to check sheds and gardens and anywhere a baby could have been secreted.

They continue to search allotments and areas of the Downs as they say the condition of the pair on arrest was consistent with people who had been spending "a significant amount of time living in the countryside".

The couple have so far refused to give any information as to the whereabouts of the two-month-old and police are holding out hope that they may have handed it into the care of a third party.

Marten, 35, and Gordon, 48, were reported missing on January 5 after their car caught fire on the M61, near Bolton.

It is believed Marten had given birth just a few days before.

They were spotted multiple times in the days that followed, including in Liverpool, Essex, south London and East Sussex.

Met Police Detective Superintendent Lewis Basford told Sky News: 

"We now have to consider the possibility that the baby has come to harm."

He said he still hoped the baby could be found alive but that the cold weather was an obvious risk to its safety.

"Clearly the risk is getting higher... this may not end in the way we would like, but we need to remain hopeful," he said.

Chief Superintendent James Collis from Sussex Police addressed the national media yesterday (Feb 28) saying his colleagues had arrived "within" minutes" of the sighting of the couple adding that his officers were supporting the Met Police with their extensive search.

He also thanked the local community for its help with the search and their patience with the heavy police presence in the area.

DS Lewis Basford added that police would be investigating the couple's reasons for traveling to Sussex.

Update: March 1, 3pm

Police searching for a missing baby have announced they have applied to Brighton Magistrates to keep parents Constance Marten and Mark Gordon in custody for a further 36 hours.

In a press conference DS Basford told reporters that the search had continued today in Newhaven and open areas to the north and east of Brighton, including the South Downs. 

He added that the public can expect to see search teams continuing their work for the foreseeable future.

CS Collis added there would be additional search parties, extra patrols and house-to-house enquiries and he asked members of the public to continue to be vigilant.

The number to call with information: 0208 345 3865 /or 999 in an emergency.

UPDATE: The latest picture received sent to our newsroom shows a policeman guarding a cordoned-off area in woodland.

Photos by Eddie Mitchell