- UK PM Boris Johnson said he was shocked, appalled and deeply saddened" after the incident
- 3 French patrol boats were joined by a French helicopter and a British helicopter in searching area
- The number of migrants using small boats to cross the channel has grown sharply this year
At least 20 migrants died on Wednesday when their boat crossing the Channel from France to England sank off the northern port of Calais. Authorities termed it the deadliest single disaster on the intensively-used route.
British and French authorities were searching the area using helicopters and coast guard vessels, according to the French maritime agency for the region.
A French naval boat spotted several bodies in the water and retrieved an unidentified number of dead and multiple injured, including some who were unconscious, a maritime authority spokesperson said.
The nationalities of the victims weren't immediately released.
The number of migrants using small boats to cross the Channel has grown sharply this year, despite the high risks that are worsening in autumn weather.
UK Prime Minister Boris Johnson said he was "shocked, appalled and deeply saddened" after a boat carrying migrants capsized in the English Channel while attempting to cross from France to Britain.
Jean-Marc Puissesseau, who is the head of the ports of Calais and Boulogne, told The Associated Press that he spoke to one of the rescuers, who said as many as 30 people had died.
(With inputs from AP)