PARIS — At least 27 migrants died while trying to cross the English Channel from France to Britain on Wednesday, making it one of the deadliest incidents on a dangerous route.

French Interior Minister Gérald Darmanin said in a news conference that 31 bodies had been recovered, including five women and a small girl, while two people survived. But his ministry told French media outlets later that the number of dead had been revised to 27.

One person was thought to be unaccounted for when a search-and-rescue operation involving ships and helicopters was called off late Wednesday night.

“Today is a [day of] great national mourning for France, and for Europe, and humanity,” Dar­manin said.

Both French and British officials focused the blame on human traffickers, though migrant crossings are also a point of contention in the post-Brexit tussle between Paris and London. Four suspects who might be connected to the incident had been apprehended, Darmanin said.

The International Organization for Migration said Wednesday’s drowning amounted to the largest known loss of life in the Channel since the U.N.-affiliated group started recording data in 2014. At least 15 more people have died at other points in 2021, as attempts to cross have increased.

Wednesday’s incident occurred off the coast of Calais, France, in the Dover Strait, where the Channel narrows to 21 miles across. That’s one of the world’s busiest shipping lanes. It can also be dangerous for people in small flimsy boats when hammered by strong currents and high winds.

Wednesday’s weather forecast, though, was for fairly calm seas and light and variable winds. Local fishermen told Reuters that more migrants than usual had tried to set out, to take advantage of the conditions, though the water remained extremely cold.

Officials did not release any information Wednesday about the nationality of those who drowned. Lille Prosecutor Carole Etienne told the Associated Press that officials were still working to identify the victims and that the investigation may involve multiple countries.

Aid workers say many of the people who try to make the journey are fleeing conflict — in Afghanistan, Iran, Syria, Iraq, Sudan, Eritrea, Yemen and elsewhere. Some want to get to Britain to reunite with family, or because they speak English and hope that will help them find work.

Since 1999, at least 300 people have died attempting to cross, according to the Institute of Race Relations, a British think tank.

French Prime Minister Jean Castex called Wednesday’s incident a “tragedy” and condemned human traffickers who “exploit the distress and misery” of migrants.

The regional prosecutor opened an investigation into aggravated manslaughter, organized illegal migration and other potential charges.

French President Emmanuel Macron said in a statement that “France will not let the Channel become a cemetery.” He called for more action at the European level, including an emergency meeting of European ministers and an “immediate reinforcement” of the European Border and Coast Guard Agency’s resources.

From Downing Street, British Prime Minister Boris Johnson called the drownings “appalling.”

“What this shows is that the gangs who are sending people to sea in these dangerous crafts will literally stop at nothing,” Johnson said.

He added that efforts by France to slow the human smuggling, with $70 million in new funding from Britain to help patrol the beaches, “haven’t been enough.”

“Our offer is to increase our support, but also to work together with our partners on the beaches concerned, on the launching grounds for these boats,” Johnson said.

“Because there is no doubt at all that the gangs concerned, unless they are shown that their business model won’t work, that they can’t simply get people over the Channel from France to the U.K., they will continue to deceive people, to put people’s lives at risk and, as I say, to get away with murder,” he continued.

France’s interior minister called the British government’s spending on stopping Channel smugglers “minimal.” He also recently complained the British government was using France as a “punchbag” while failing to address its unregulated labor market.

Macron, in his statement on Wednesday, defended French efforts, saying that more than 1,500 traffickers had been caught in the region since the beginning of the year.

French police also regularly clear — in a way that draws complaints from migrants and human rights groups — the makeshift camps on the northern coast, where people gather before attempting to cross the Channel.

Still, nearly three times as many migrants have crossed by sea this year compared with last year. Earlier this month, 1,185 people ventured across in a new daily record that the British Home Office described as “unacceptable.”

Conservative Party lawmakers have urged the British government to “take back control” of the Channel. Critics have compared the scene to the U.S.-Mexico border, decrying what they see as a too-soft approach to illegal immigration.

In response, Home Secretary Priti Patel recently authorized tough new tactics to push boats back toward France. That policy, however, has not been implemented. Such aggressive moves could violate maritime law and endanger lives, if migrant vessels were unseaworthy and in distress.

Natalie Elphicke, a Conservative lawmaker for Dover, called Wednesday’s incident an “absolute tragedy” and said it highlighted why “saving lives at sea starts by stopping the boats entering the water in the first place.”

“As winter is approaching the seas will get rougher, the water colder, the risk of even more lives tragically being lost greater,” she said.

Pro-Brexit campaigner Nigel Farage, now a host on GB News, has warned that Johnson’s government is ignoring the crossings and opening England’s beaches to illegal immigration.

In a column in the Daily Telegraph on Monday, Farage warned, “the migrant crisis is out of control, and the Prime Minister doesn’t seem to care.”

As it turns out, Farage himself was out in a boat in the English Channel on Wednesday, filming migrant vessels and tweeting, as he prepared for an evening broadcast.

Responding to the increase in recent crossing attempts, a sporting goods company last week stopped selling kayaks in its shops in northern France.

But drowning at sea is not the only way that migrants have died trying to reach Britain. Others have been killed trying to board trucks, containers and trains, traveling either via ship or through the Channel Tunnel.

In 2019, 39 Vietnamese migrants were found dead in a shipping container, having suffocated on their journey by sea ferry and truck hauler from Zeebrugge in Belgium to Purfleet in southeast England. Two of the smugglers were convicted of manslaughter and sentenced to 20 and 27 years.

Pham Thi Tra My, 26, was among the victims. She sent a heartbreaking text message to her mother when she was in the container, en route to England. “Mom, I love you. I’m dying, I can’t breathe,” she wrote.

Adam and Booth reported from London. Ellen Francis in London contributed to this report.