GRANDE-SYNTHE, France (AP) — Authorities and aid workers are searching for several hundred migrants who disappeared after a fire ravaged their camp in northern France, a shocking blaze that exposed anew the challenges and tensions around Europe's migrants just 12 days before France's presidential election.

Police cordoned off the largely destroyed camp in the Dunkirk suburb of Grande-Synthe on Tuesday and investigators inspected the site to try to determine the cause of the Monday night fire, which broke out following a fight between rival groups of migrants.

Three mobile police units were deployed in the area to head off tensions prompted by the camp's demise, the government said in a statement. The interior and housing ministers headed to the scene in a sign of the government's concern about the issue.

Most of the camp near the English Channel is now reduced to the charred remains of wooden shelters and sparse belongings of the migrants, who converged on northern France in hopes of reaching Britain as part of waves of recent migration to Europe.

As many as 1,600 people were in the camp when the blaze broke out, according to Grande-Synthe Mayor Damien Careme and prefect Michel Lalande, the top government official for the region. Some 500 were taken to three local gymnasiums, including one set aside for children and families — but most of the other migrants remain unaccounted-for, the mayor and prefect told reporters Tuesday.

Doctors Without Borders, which set up the site a year ago to replace filthy makeshift camps in the region, is holding meetings Tuesday to decide what to do next. Other aid groups are planning to distribute meals Tuesday to migrants in the gymnasiums and anywhere else they are found around town.

The first priority is to find migrants dispersed by the blaze, said Corenne Torre, head of the humanitarian group in France.

"We just don't know where they are," she told The Associated Press. She estimated that at least 600 migrants remain unaccounted-for. Some are believed to be hiding because they fear the authorities or because they fear rejoining a camp with rival gangs, she said.

She said that 10 migrants are in local hospitals with light injuries following the fire.

The prefect and mayor said authorities believe the fire was set intentionally and was linked to a fight earlier Monday between Kurdish and Afghan migrant groups involving up to 150 migrants.

The camp will remain closed during the investigation, and local authorities will consider whether to open a new camp to replace it.

It's a sensitive issue in France ahead of the two-round April 23-May 7 presidential election in which immigration is a key issue. Far-right candidate Marine Le Pen and conservative candidate Francois Fillon reiterated calls Tuesday for stricter border controls.

The prefect took the opposite stance.

"The issue today is to shelter those people who live outside at the moment, and to build a future for them," Lalande told reporters. France sheltered migrant populations in the past, he said, "so we are not going to stop the march of history. To the contrary, it is in the name of this history that we are going to build a future for these people."

"I lost all my documents," said an Iraqi migrant who identified himself only as Albidani, standing outside the camp. "I just have only this paper that says I'm a refugee in France."

"We are refugees here in France. We don't have any place. ... We don't know what to do. We lost everything," Albidani said.

Charlton reported from Paris. Thomas Adamson in Paris contributed.