CALAIS, France (REUTERS) - Migrants at the "Jungle"camp in Calais set more tents and shelters ablaze on Wednesday (Oct 26) and an explosion rocked the site, while others queued to be resettled around France by officials clearing the camp.

Riot police spread out around the camp and fire trucks moved in to put out some of the fires, which sent towering plumes of smoke into the sky above the squalid and unsanitary camp that at one point housed more than 6,000 people.

Regional prefect Fabienne Buccio said camp clearing, which began on Monday, could be completed by the end of the day, BFMTV reported.

"The operation will continue today to remove the empty shelters and to avoid them being set fire to again," a local government spokesman told France Info radio as dawn broke to reveal the smouldering remains of what had once been one of the camp's main thoroughfares.

Local opposition to the makeshift camp, along with criticism from right-wing politicians, stung the French government into launching the clearing operation.

More than 4,000 migrants, who had come to Calais hoping to cross the short stretch of sea to Britain by trying to leap on trucks and trains or walk through the tunnel, have been bussed out of the camp so far and relocated around France.

Wednesday's explosion may have been a bursting gas bottle, like blasts that accompanied fires of scrap wood, plastic and fabric overnight. One person was slightly injured by those earlier explosions.

Late on Tuesday, Buccio said it was difficult to prevent the fires, which became something of a ritual earlier this year when one section of the camp was dismantled.

"Some migrants follow traditions - we asked them not to do it - but they set ablaze their tents and their shelters when they leave," she said.

People fleeing poverty and war outside Europe have over the past few years congregated at Calais, the main port of entry to Britain from France.

They have continued to come despite the high fences built over past months to keep them from crossing, and despite Britain's refusal to accept the vast majority of them.

A separate facility has been set up for children who may be accepted by the British government.

As the queue of mostly male adults formed outside a processing centre, some refused to accept that their dream of reaching Britain was over.

Hamid, 30, from Afghanistan, said he had been among those setting fire to shelters. "We don't care about problems that are to come after this. We did it because we don't want to stay in France," he said. "We want to go to England and England only. It doesn't matter if I go to jail here."