Police in Italy believe traffickers made some $3m (£1.9m; €2.5m) from 359 illegal migrants found abandoned on a cargo ship in the Mediterranean.
The Ezadeen was towed into the Italian port of Corigliano Calabro after being found by coast guards on Friday.
Most of those aboard appear to be Syrians, in the second such case involving a freighter this week.
The ships reportedly started in Turkey and Turkish-controlled northern Cyprus, in a change from the Libyan route usually favoured by gangs.
The police chief of Cosenza province, Luigi Liguori, said each migrant had paid between $4,000 and $8,000 to board the ship.
Officers say that the smugglers wore hoods and locked the migrants in the ship's hold before apparently abandoning ship on a lifeboat.
In the earlier case, Italian coastguards boarded a ship, the Blue Sky M, carrying 796 migrants on Tuesday. Finding it without a crew, they steered it into the south Italian port of Gallipoli.
The smugglers' new tactic appears to be simple and effective: point a cargo ship towards Italy and let the coastguard pick it up, the BBC's James Reynolds reports from Corigliano Calabro.
Illegal migration to the EU has been fuelled by the civil war in Syria, which has driven people to seek asylum in Europe, along with economic migrants.
Last year it is estimated that nearly 3,500 refugees died trying to cross the Mediterranean while another 200,000 were rescued.
The Ezadeen, an ageing Sierra Leone-flagged ship originally used to transport cattle, was spotted on Thursday evening and arrived in port in Italy on Friday night.
Passengers are said to be in good condition and are being transferred to immigration centres and foster homes across Italy, according to coastguard and police officials.
Mr Liguori says the new tactic used by the criminal gangs is attracting better-off migrants.
"We've noticed a change in the make-up of the Syrian refugees on board," he said. "They are socially well off. They wear better clothes and are also better organised and, if you allow me to, they are less desperate than the migrants we normally see."
Dimitris Avramopoulos, the EU's commissioner for migration, called for "decisive and coordinated EU-wide action" against the people traffickers.
"Smugglers are finding new routes to Europe and are employing new methods in order to exploit desperate people," he said, promising to present a "comprehensive approach on migration".
Illegal migrants arriving in the EU are assessed to see if they have a valid claim for asylum. They must satisfy the authorities they are fleeing persecution and would face harm or even death if sent back to their country of origin.
Passengers from the Blue Sky M have also reportedly been dispersed to reception centres around Italy.
Tommaso Tomaiuolo, a local resident in the Gallipoli area, saw the ship when it docked in the early hours of New Year's Eve and later talked to some of the migrants through the gate of a local school where they were taken.
Mr Tomaiuolo told BBC News that one Syrian migrant, who asked for his name not to be given, told him he had paid "Turkish mafia" 7,000 euros for himself and 7,000 euros for his pregnant wife to make the journey.
The 35-year-old said he was scared to reveal his identity in case he was returned to Turkey, where he had been living for about a year.
He spoke fluent English and said he had lived previously several times in the UK. He and his wife, he told Mr Tomaiulo, left Turkey on 21 or 22 December, apparently starting the journey in the port of Mersin in a smaller boat.
He gave Mr Tomaiuolo a photo from his mobile phone which shows the hold of a ship packed with people during the crossing on the Blue Sky M.