A runaway aristocrat and her partner were arrested after a month on the run in England. Police have no idea what happened to their newborn baby.

• UK police have arrested a couple for suspicion of child neglect.
• Police have begun an urgent search operation for the couple's baby, which has yet to be found.

Police this week arrested a British aristocrat and her partner on suspicion of child neglect after a month on the run across England, but investigators have no idea what happened to the couple's newborn baby, according to multiple reports.

Constance Marten, the 35-year-old daughter of aristocrat Napier Marten, who has close ties to the royal family, went missing in early January with her partner, Mark Gordon, a 48-year-old convicted sex offender, according to the BBC.

A spokesperson for the UK's Metropolitan Police service told CNN that investigators believe that Marten gave birth to a child days before her disappearance. The spokesperson said police believe the child did not receive medical care, leading investigators to suspect child neglect.

The couple went missing after their car burst into flames on the side of a highway near Manchester on January 5, CNN reported, citing police. CNN reported that the couple then spent weeks taking taxis across the country, sleeping in a tent in various locations, and disguising themselves to prevent being recognized on CCTV cameras.

After a nearly two-month-long search for the couple and their baby, police found the couple in Brighton in southern England when a local resident spotted them, CNN reported. The baby was not with them when police arrested the couple.

Police have now launched an "urgent search operation" for the baby, telling locals to check in sheds and outhouses for signs of the baby, the BBC reported. Police are concerned that the baby has been exposed to extremely cold temperatures, The Guardian reported.

"The arrest location was close to open land and the couple were moving towards that land," Detective Superintendent Lewis Basford, who's leading the investigation, said, told journalists this week, according to the BBC. "We know that they travel, we know they travel long distances."

"For whatever reasons she and her partner went on the run, the consequences of their actions have increased many fold," Marten's father, Napier Marten, told The Independent. "When the time comes, I am longing to see Constance, to reassure her that, whatever the weather, I love her dearly and will support her as best I can through the difficult weeks and months here on in."

Napier Marten declined to comment on the situation to Insider.