Charities report hunger strikes and absconding among the 1,600 children and young people evacuated from the Calais 'jungle' camp to centres across France where many are kept unaware of the progress of their applications to join relatives in Britain.
Some have headed for Grande-Synthe refugee camp at Dunkirk but many migrants are sleeping in ditches near coast and still trying to reach UK.
French interior minister Bernard Cazeneuve says Britain has agreed to take in 'several hundred' of the around 1,600 child migrants in the town.
Officials say rise in number of people living on street in capital could be linked to the demolition of so-called 'Jungle' migrant camp in Calais.
French ministers have hit back at apparent British criticism of way migrant children are being treated while Calais camp is dismantled.
But charities said many unaccompanied minors at the camp had not been processed and reporters said groups of adults remained in area.
A number of migrants 'followed tradition' and set ablaze their tents and their shelters when they left, says local French official.
Officials say demolition will start by hand and bulldozers will not roll in immediately in an effort to minimize tensions as evacuation continues.
After sporadic unrest overnight, migrants waited with calm resignation to be relocated by bus in France while asylum requests are considered.
More than 1,200 police and officials have begun operation to clear the 'Jungle' migrant camp in Calais which has been housing 7,000 people.
With the expected dismantlement of the 'jungle' migrant camp in Calais to begin as of Monday morning, the French authorities step up attempts with UK counterparts to save children who have right of entry into Britain from being herded with adults into centres around France amid 'chaos' of evacuation.
The evacuation and subsequent demolition of the makeshift camp estimated to shelter up to 10,000 migrants attempting to reach Britain in clandestine crossings of the English Channel will begin on October 24th, the French authorities have announced, when thousands of migrants will be bussed to refugee centres around France.
The veteran French conservative Alain Juppé, who is currently favourite for his party's nomination to run as presidential candidate in elections next year, has said France can no longer tolerate the situation in Calais where thousands of migrants hoping to enter the UK are stranded, and called for Le Touquet agreement to be scrapped.
A demand by several Conservative MPs that unaccompanied minors allowed to join relatives in the UK from the Calais 'Jungle' migrant camp be screened by dental checks to ensure they are not adults was rejected as an 'inaccurate, inappropriate and unethical' method by the British government.
A TV crew filming migrants apparently awaiting an opportunity to stow away in trucks at a service station near the Channel port were set upon last Thursday evening in what they believe was probably an attack motivated by a people smuggler who was on the images.