A newborn baby who has gone missing with her parents is "less than a week old", police have said.
Officers are desperately trying to track down Constance Marten and Mark Gordon who disappeared after their car broke down near Bolton last Thursday.
Ms Marten is believed to have recently given birth and police said neither she nor the baby had been seen by doctors.
In his latest update, Det Ch Insp Rob Huddleston confirmed the infant was "less than a week old", meaning the new mother would have given birth within hours of the breakdown on the M61.
From there, the family travelled via Liverpool to Essex with sightings at Harwich port at 9am on Saturday and in Colchester an hour later.
Det Ch Insp Huddleston said he did not believe they had tried to leave the country and it remained unclear why they did not want to be found.
"We don't know why they might be avoiding detection," he said. "We know they have travelled from Manchester through Liverpool and down into Essex. Why that is, we don't know.
"We have already spoken to the ports and they haven't made any effort to go through Harwich."
Police have appealed directly to Ms Marten to come forward and get herself and her baby checked over by medics.
"To you, Constance, medical professionals still need to assess your baby to make sure he or she is medically well and there no underlying issues for which he or she may need help for," said Det Ch Insp Huddleston. "Indeed, medical professionals would like to examine you for the same reasons.
"Please, get in contact any way you would like to. We are here and ready to help you."
Police spent Monday night visiting every B&B and hotel in Colchester to try to establish where the couple have been staying and are in contact with transport operators to work out if they have left the city.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know