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LONDON (AP) — British police said Tuesday they have launched a major search for a two-month-old baby after officers arrested the infant’s mother and her boyfriend who had been missing since January.

Aristocrat Constance Marten, 35, and her boyfriend Mark Gordon, 48, a convicted sex offender, had been on the run since the baby was born in early January. They have been spotted around the country, and police said they sought to avoid being detected by paying for everything in cash and covering their faces when on CCTV.

Marten and Gordon were arrested on suspicion of child neglect late Monday in Brighton in southern England after a tipoff from a member of the public. The baby was not with them, and police launched an “urgent” search operation in the area.

“It is a vast area and at present we are looking in the local vicinity to where the couple were arrested last night, seeking a shelter or location for where they may have been holed up and hopefully where the baby is present,” Detective Superintendent Lewis Basford told the BBC.

Police searched for Marten and Gordon for weeks after a car they were travelling in was found on fire on the side of a highway on Jan. 5.

Police believe Marten had given birth either in or near the car just a day or two earlier, and officers said they were increasingly concerned for the family’s welfare because neither Marten nor the baby had been seen by medical professionals.

Dozens of officers were involved in the search, and more than 600 hours of CCTV footage were reviewed.

Marten, who is from a wealthy, aristocratic British family, was reportedly a drama student when she met Gordon. He had served 20 years in prison in the United States after being convicted in Florida of kidnapping and sexual battery, according to U.S. law enforcement records. He was deported from the U.S. after his release.