Dozens of people plunged into the treacherous waters of the busy channel on Tuesday.
“Unfortunately, the bottom of the boat ripped open,” said Olivier Barbarin, mayor of Le Portel near the fishing port of Boulogne-sur-Mer, where a first aid post was set up to treat victims.
A maritime rescue official who spoke on condition of anonymity because he was not authorised to discuss details of the operation confirmed at least 13 migrants were dead.
Etienne Baggio, a spokesman for the French maritime prefecture that oversees that stretch of sea, said “more than 10” people were dead but he didn’t have an exact number. The prefecture said the boat got into difficulty off Gris-Nez point.
Both Baggio and the mayor said rescuers recovered 61 people from the waters.
Sea temperatures off northern France were about 20 degrees.
At least 30 migrants have died or gone missing while trying to cross to the UK this year, according to the International Organisation for Migration.
At least 2109 migrants have tried to cross the English Channel on small boats in the past seven days, according to UK Home Office data updated Tuesday. The data includes people found in the channel or on arrival.
Europe’s increasingly strict asylum rules, growing xenophobia and hostile treatment of migrants have been pushing them north.