Sixty-four migrants "including a pregnant woman and children" were rescued Saturday in the English Channel after their improvised boat found itself "in trouble" off Dunkirk, French authorities said.

Several of the people "appeared to be in a state of hypothermia" after being brought aboard a patrol ship, the French prefecture in charge of the Channel and North Sea said in a statement.

First responders and border police took charge of the migrants, who were "all safe and sound" when they were put ashore in Calais in the early evening, it added. Calm weather prompted fears among rescuers that larger numbers would attempt the crossing to Britain.