PARIS • At least 31 migrants bound for Britain died Wednesday when their boat sank in the English Channel, in what France’s interior minister called the biggest tragedy involving migrants on the dangerous crossing to date.

Interior Minister Gerald Darmanin said 34 people were believed to have been on the boat. Authorities found 31 bodies and two survivors, and one person appeared to still be missing. The nationalities of the travelers was not released.

A joint French-British operation to search for survivors was still under way late Wednesday.

Four suspected traffickers were arrested Wednesday on suspicion of being linked to the sunken boat, Darmanin told reporters in the French port city of Calais. He said two of the suspects later appeared in court.

The regional prosecutor opened an investigation into aggravated manslaughter after the sinking.

“It’s a day of great mourning for France, for Europe, for humanity to see these people die at sea,” Darmanin said.

He called for coordination with the U.K., saying “the response must also come from Great Britain.”

Noting other deadly past incidents involving migrants in the same waters, Darmanin lashed out at “criminal traffickers” driving thousands to risk the crossing.

British Prime Minister Boris Johnson convened a meeting of the government’s crisis committee, and Darmanin rushed to see survivors in a Calais hospital. The two governments have long been at odds over how to prevent the crossings, with both sides blaming the other for not doing enough.