London (CNN)British police have arrested an aristocrat and her partner after the pair went missing with their newborn baby in early January, but the search for the infant continues.
In an update Tuesday, London's Metropolitan Police said in a statement that Constance Marten, 35, and Mark Gordon, 48, had been "initially arrested on suspicion of child neglect," but were later "further arrested on suspicion of gross negligence manslaughter."
Police said that the couple's baby, whom they believe was born just before the pair disappeared without receiving medical attention, is still missing.
"Throughout this investigation our key priority has been finding the baby, and we remain committed to that," Detective Superintendent Lewis Basford said in the statement.
Police helicopters, sniffer dogs, thermal imaging cameras and drones are all being used to assist the over 200 officers on the ground in their search for the baby, the police statement added.
Prior to their arrest, the couple were spotted in Brighton, southern England, on Monday night, police had said earlier on Tuesday.
Basford said a member of the public there "quickly called police" on Monday night after spotting the couple, enabling police to get "on the scene within minutes to make the arrest."
He also appealed to residents of the area to report any potential sightings or information about where the couple may have slept.
The search for the couple and newborn began in early January, with