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."
Siddiq, a 16-year-old Afghan who said he arrived in the camp in northern France 10 months ago, sat on the icy tarmac with two friends, sheltering under a blanket, after spending the night under a bridge.
"Our tents were burning. Someone set fire to them, though I don't know who," he said.
"I have seen many fires before but not like this. First there was a gas canister that exploded, boom! Like a bomb," he said.
"Then in the middle of the night my neighbour's tent caught fire. I ran out," said Siddiq.
The trio queued outside a registration centre where they hoped to be interviewed later to make their case for being allowed into Britain.