BOULOGNE-SUR-MER, France — A boat carrying migrants ripped apart in the English Channel as they attempted to reach Britain from northern France on Tuesday, plunging dozens into the treacherous waterway and leaving 12 dead, authorities said.

Most of the victims were believed to be women, some under 18, and many of the passengers didn’t have life preservers, officials said, with one calling it the deadliest migrant accident in the channel this year.

“Unfortunately, the bottom of the boat ripped open,” said Olivier Barbarin, mayor of Le Portel near Boulogne-sur-Mer, where a first aid post was set up to treat victims. “If people don’t know how to swim in the agitated waters … it can go very quickly.”

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Europe’s Strict Asylum Rules Push Migrants North

Europe’s increasingly strict asylum rules, growing xenophobia and hostile treatment of migrants have been pushing them north. Before Tuesday’s accident, at least 30 migrants had died or gone missing while trying to cross to the U.K. this year, according to the International Organization for Migration.

Rescuers pulled a total of 65 people from the English Channel on Tuesday in a search that lasted more than four hours, according to Lt. Etienne Baggio, a spokesman for the French agency that oversees the stretch of sea where the boat ripped apart. Doctors confirmed 12 died, he said.

Another 12 people were hospitalized, and two were in very serious conditions, authorities said.

Adam Beernaert, director of the Civil Protection authority, whose personnel looks after rescued migrants once they reach land, said the people his team attended Tuesday were traumatized. “What needs to be said is that they shouldn’t cross,” Beernaert told the AP. “The sea is not easy. Weather conditions change all the time.”

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Deadliest Migrant Boat Tragedy in English Channel This Year

Baggio called it the deadliest migrant boat tragedy in the English Channel this year. In July, four migrants died while attempting the crossing on an inflatable boat that capsized and punctured. Five others, including a child, died in another attempt in April. And five dead were recovered from the seas or found washed up along a beach after a migrant boat ran into difficulties in the dark and winter cold of January.

Many of those aboard the vessel that broke up in the English Channel on Tuesday didn’t have life vests, Baggio said. He said the boat was an inflatable. Three helicopters, a plane, two fishing boats and more than six other vessels were involved in the rescue operation.

In another sea tragedy Tuesday involving migrants seeking a better life in Europe, a boat carrying migrants capsized in the Mediterranean off the Libyan coast, leaving one person dead and 22 missing, Libyan authorities said.

The agency overseeing the rescue operation in the English Channel said the boat got into difficulty off Gris-Nez point between Boulogne-sur-Mer and the port of Calais further north. Sea temperatures off northern France were around 20 degrees C, or about 68 F.

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French and British Authorities Respond to Tragedy

Interior Minister Gerald Darmanin went to Boulogne-sur-Mer to meet those involved in handling what he described as the “terrible shipwreck.” He said the boat was frail and small — less than 7 meters (23 feet) long — and that smugglers are packing more and more people aboard such vessels. Most of the people on the boat were believed to be from Eritrea, and most of the victims were women, he said.

Last week, the leaders of France and the U.K. agreed to deepen cooperation on illegal migration in the channel.

“We absolutely must — and this is a very important point — re-establish special relations with our British friends,” Darmanin said on Tuesday. He later told the AP that to successfully tackle smuggling networks, immigration legislation between the U.K. and France should be harmonized.

“It has now been 30 years that these problems remain, and it is absolutely necessary that we find solutions,” said Barbarin, the mayor of Le Portel.

U.K. Home Secretary Yvette Cooper called it “a horrifying and deeply tragic incident” and paid tribute to French rescuers “who undoubtedly saved many lives, but sadly could not save everyone.”

“The gangs behind this appalling and callous trade in human lives have been cramming more and more people onto increasingly unseaworthy dinghies, and sending them out into the Channel even in very poor weather,” she said.

“They do not care about anything but the profits they make, and that is why — as well as mourning the awful loss of life — the work to dismantle these dangerous and criminal smuggler gangs and to strengthen border security is so vital and must proceed apace.”

At least 2,109 migrants have tried to cross the English Channel on small boats in the past seven days, according to U.K. Home Office data updated Tuesday. The data includes people found in the channel or on arrival.