Four migrants trying to cross the Channel to Britain died in French waters in the early hours of Sunday, a spokesperson for the local prefecture told Reuters.
The small boat overturned as it attempted to launch from a beach, the official said, adding that one person in critical condition had been taken to hospital in Boulogne, northern France.
Local newspaper La Voix du Nord said about 70 people were trying to get into a small boat and dozens were pulled from the cold water during overnight rescue efforts in Wimereux, south of Calais.
Those dead are believed to be Iraqi and Syrian, La Voix du Nord said.