Four migrants died Tuesday after the boat in which they had set out from France to try and reach Britain capsized in the English Channel, a French official said.
One man drowned when the boat sank, and three people died after they were pulled from the water alive with 14 others, said the official of the Nord department.
Some of those rescued had gone into cardiac arrest, and others suffered hypothermia.
The group's small fishing boat capsized in the Channel at about 9:30 am, official Herve Tourmente told journalists earlier in Loon-Plage, near Dunkirk.
"It seems that one person, who might be an infant, is still missing," Tourmente said, noting that stormy conditions had made the attempted crossing especially perilous.
A growing number of migrants have tried to cross the busy shipping lane for Britain in recent months, with four deaths recorded in 2019 and now seven so far this year.
In September, French authorities said they had intercepted over 1,300 people trying to reach the UK, including a handful who attempted to swim across the Channel.
Northern France has long been a magnet for people seeking to smuggle themselves to Britain in small boats or in one of the tens of thousands of trucks and cars that cross over daily on ferries and trains.
The issue has been a source of tension, with Britain accusing France of not doing enough to stop the crossings.
French authorities insist they are doing all they can.