“Against a pattern of increased abuses against asylum seekers in recent years, this newest approach stands out,” said Itamar Mann, an expert in maritime and refugee law at the University of Haifa in Israel. “Its methods chillingly resemble organized crime, and indeed the operations of people smugglers, which European policymakers so adamantly denounce.”

“The facts available raise serious concerns that we are seeing the emergence of a novel systematic pattern, such that may even put Maltese state officials in danger of criminal liability, at home or abroad,” Dr. Mann added.

The Maltese government did not respond to multiple requests for comment.

The activity was first documented on the evening of April 12, when three aging blue trawlers left the Grand Harbour in Valletta, the Maltese capital, within an hour of each other. The three boats — the Dar Al Salam 1, the Salve Regina and the Tremar — departed at the request of the Maltese authorities, according to the captain of the Tremar, Amer Abdelrazek.

A former Maltese official, Neville Gafa, said he was enlisted by the government that same night to use his connections in Libya to ensure the safe passage of the first two boats to Libya.

The boats did not submit paperwork to the immigration police, and switched off their satellite tracking devices soon after leaving port, maritime databases show.

But their mission had already been determined, said Mr. Gafa, who said he had been asked by the Maltese prime minister’s chief of staff, Clyde Caruana, to help coordinate the operation. Mr. Caruana did not respond to requests for comment, but a government spokesman told The Times of Malta that Mr. Gafa had been asked to liaise with Libya on a separate matter that was unconnected to the episode.

The trawlers were sent to intercept a migrant vessel attempting to reach Malta from Libya — and which had been issuing mayday calls for some 48 hours — and then return its passengers to Libya, Mr. Gafa said.