Around 500 people, mainly Iraqi Kurds, had been living at the wooded site in Loon-Plage, near a canal that often serves as a key launching point for boats hoping to cross the English Channel for Britain.
Buses stood by to bring the migrants to shelters, but most left instead on foot, carrying what belongings they could.
On Monday night, one migrant was shot and killed and another wounded by what volunteer aid workers described as machine gun fire, the day after two others were also shot and wounded, one seriously.
Ammunition from “weapons of war” were found, Dunkirk’s state prosecutor Sebastian Pieve had told AFP on Tuesday, and a clash between rival smuggling groups was “a theory, but it’s not easy to establish”.
“But it’s certain that human trafficking is the backdrop to this,” he said.
Dawan, a 32-year-old Kurd, would say only “mafia, mafia” when asked by AFP about the shootings.
He said he had recently paid €1,600 to a smuggler who said he would get him to England after spending five months in France, but the man disappeared the next day.
Claire Millot of the Salam migrant aid group said most volunteer associations had quit operating at Loon-Plage out of security fears, adding that Africans and other nationalities had recently been seen in an area usually occupied mainly by Kurds.
More than 7,000 migrants have managed to cross the busy shipping lane and reach the British coast since January, after the number of arrivals tripled to over 28,000 last year — which saw at least 30 migrants die while trying.