Two more people are “potentially missing”, the regional maritime prefecture told AFP. A total of 66 people were retrieved from the boat, including the two casualties, it added.

Among those recovered, “one unconscious victim, in critical condition, was taken by helicopter to the hospital in Calais” while a second “could not be revived”.

The critically hurt person’s condition later stabilised, a source familiar with the case told AFP.

French sea rescue coordinators at Gris Nez, near the northern port city Calais, were warned during the night that a migrant boat was in difficulty less than eight kilometres (five miles) from the coast.

A rescue vessel arrived in the area at around half an hour after midnight (CEST), maritime authorities said.

After the crew found one of the migrant boat’s buoyancy tubes “deflated” and people “in the water”, they brought everyone they could find back to Calais.

Another person was seriously hurt in a separate Channel crossing attempt Friday morning off Sangatte, just outside Calais, local authorities said.

Boats and aircraft are still looking for remaining survivors, while French Interior Minister Gerald Darmanin is expected in Calais on Friday morning on a previously scheduled visit.

The region around Calais, the jumping-off point for the shortest Channel crossing to Britain, has long been a hotspot for migration.

Two decades after the closure of a Red Cross centre in Sangatte, hundreds of people still live in tents and makeshift shelters near Calais and Dunkirk, hoping for an opportunity to make the crossing hidden in a truck or aboard a small boat.

Small boats are a political priority for the British government, as tens of thousands of people a year have been making the dangerous crossing.

The human toll has been high, with one of the worst-ever sinkings two years ago claiming 27 lives.

French security forces’ attempts to thwart the migrants before they take to the water “have done nothing but increase the risk, distress and deaths”, migrant aid group Utopia 56 wrote on X (formerly Twitter).

The issue has become a huge political controversy for Conservative Prime Minister Rishi Sunak, who wants to implement a contested scheme to deport arriving migrants to Rwanda as a deterrent.

Maritime authorities say nine people have been killed in migrant Channel crossings so far this year.

In late November a migrant boat carrying 60 people sank, drowning a man and woman both in their 30s. Another body found on a beach several days later may have been another passenger on the same boat.

And in August this year, six Afghans aged 21 to 34 drowned after their small boat capsized.

French authorities say that boats are increasingly overloaded, with the average number of about 53 passengers nearly double the average of two years ago.

More than 28,000 people have crossed the Channel since the start of this year, according to British government statistics running to the end of November, compared with almost 46,000 over the whole of last year.