Fires cut through a swathe of the Calais "Jungle" on Wednesday, sending migrants fleeing as French authorities prepared to ramp up demolition of the notorious camp.
The blazes spread just hours after workers protected by police moved in Tuesday to clear the squalid camp that has been home to an estimated 6,000-8,000 migrants, many with hopes of reaching Britain.
"Our tents were burning. Someone set fire to them, though I don't know who," said Siddiq, a 16-year-old boy, who was forced by the flames to sleep under a bridge at the camp's entrance.
"I have seen many fires before but not like this."
A Syrian man was taken to hospital with injuries to his ear drums after a gas canister exploded in the flames, which ravaged one of the main thoroughfares in the camp.
A local official downplayed the blazes, telling AFP: "It's a tradition among communities who set fire to their homes before leaving."
On Tuesday workers in hard hats and orange overalls used power saws to reduce shacks to piles of wood and plastic that were removed by diggers.
Mattresses, blankets, clothes, pots and suitcases left behind by migrants were also carted away.
Located next to the port of Calais, the Jungle has for years been a launchpad for migrants attempting to make it to Britain by sneaking onto lorries or jumping onto trains heading across the Channel.
As part of the camp's clearance, 3,242 adults have been transferred to centres around France since Monday and 772 unaccompanied minors have been moved to shipping containers converted into temporary shelters in the Jungle, the interior ministry said.
The numbers represent around half the camp's estimated population before the operation began, according to official figures.
The authorities have said those who agree to be moved can seek asylum in France. Those who refuse risk deportation.
The Jungle's thousand-plus unaccompanied minors have been the main focus of charities' concerns, and hundreds of anxious youths queued Tuesday for interviews with French and British officials who will decide their fate.
Britain took in around 200 teenagers in the week before the clearance began as an eleventh-hour gesture, with the transfers resuming Tuesday after a hiatus on Monday.
An AFP reporter saw a coach carrying around 30 child refugees arrive at an immigration office in the London district of Croydon.
The curtains on the bus were drawn after pictures of some teenagers reunited with family in Britain sparked accusations that they had lied about being children.
French Interior Minister Bernard Cazeneuve said Tuesday that all unaccompanied minors "with proven family links in Britain" would eventually be transferred and that London had committed to reviewing all other cases where it was "in the child's interest" to settle across the Channel.
British Interior Minister Amber Rudd on Monday pledged to bring eligible children from France to Britain "as quickly and as safely as possible", without specifying numbers.
Police in Calais have battled near-nightly attempts by migrants to reach Britain over the past year.
The town's Mayor Natacha Bouchart said seeing people queue to leave the camp was "a great relief".
But many locals fear more settlements will sprout up in the area once the Jungle is razed.
Around France, the resettlement of asylum-seekers has met with a mix of hostility and solidarity.
Villagers in the wine-making hamlet of Chardonnay gave two dozen Sudanese youths a chilly reception on Monday, while Paris and Nantes saw small pro-migrant rallies.
Back in the Jungle, Arbat, a 25-year-old Sudanese migrant, said he was ready to move on.
"I know my future is no longer here," he said, adding that he wants to marry a French woman.
"They tell me they are all beautiful. Is it true?" he joked.