As many as 1,000 young migrants remain in the makeshift French camp as the two countries argue over their future. Britain has said it only has a responsibility to take children who have family in the UK.
While French government officials insist that close to 5,000 people have been moved out of the Calais "Jungle" in northern France over the past five days, uncertainty remains over the fate of hundreds of youngsters still living in the camp even as work to demolish it is underway.
Charity workers said most of the young migrants have been put in large container-box shelters in one section of the site. But some others have not signaled their existence to authorities, making it impossible for officials to arrange the young people's departure from the camp, NGO workers added.
A tussle of responsibility over who will house the children continued on Friday between French and British authorities. French Interior Minister Bernard Cazeneuze said he expected the UK government to honor its obligation to take minors from Calais.
But his counterpart in London said it was up to France to protect migrant children still in Calais, adding that the UK's duty under EU law was limited to youngsters looking to reunite with relatives in Britain.
The UK has, so far, accepted 274 children who meet these criteria and is currently examining hundreds of other applications.
My picture of the week | Smoke over the Calais 'Jungle' camp
According to a spokesman, British Home Secretary Amber Rudd said: "Any child either not eligible or not in the secure area of the camp should be cared for and safeguarded by the French authorities.
"We understand that specialist facilities have been made available elsewhere in France to ensure this happens."
Media reports have suggested that many unaccompanied children have been sleeping rough around the French port town since the clearance of the "Jungle" began on Monday.
Dozens of youths were offered transfers out of the camp on Friday, according to the AFP news agency.
Children urged to leave
Aid workers urged them to take the last buses leaving for shelters in other parts of France, with 50 youngsters taking up the offer. Others were still hoping to be transferred to Britain.
A spokesman for the UN refugee agency (UNHCR) said on Friday that the agency had asked that "special arrangements be made to ensure the safety and welfare of children in the "Jungle" before it closed.
"We are continuing to work to identify and protect children and other individuals with special needs in Calais," spokesman William Spindler said in a statement.
On Friday, demolition teams resumed tearing down the makeshift dwellings where around 6,400 people, mostly Afghans, Sudanese and Eritreans, had been living, according to official estimates.
But many locals fear new settlements will simply spring up in the area after the "Jungle" is completely razed.