Two men were found guilty of manslaughter of 39 Vietnamese nationals who were found dead in a lorry trailer in Essex.
The migrants suffocated in a sealed container en route from Zeebrugge to Purfleet in October 2019.
Eamonn Harrison, 24, who dropped off the trailer at the Belgian port, and Gheorghe Nica, 43, were convicted by an Old Bailey jury.
Two others were convicted of being part of a wider people-smuggling conspiracy.
The trial examined three smuggling attempts by the gang, in which two were successful on 11 and 18 October, and the final trip on October 23.
Lorry driver Christopher Kennedy, 24, from County Armagh, collected the trailers from Purfleet on the earlier two runs, claiming he thought he was transporting cigarettes.
But the jury found Kennedy and Valentin Calota, 38, of Birmingham, guilty of conspiring to assist illegal immigration.
Another two men Ronan Hughes, 41, and 26-year-old lorry driver Maurice Robinson had previously admitted manslaughter.
Prosecutors said in the fatal run, the container became a “tomb” as temperatures in the unit reached an “unbearable” 38.5C.
The migrants were sealed inside for at least 12 hours.
Harrison, of Newry, County Down, towed the trailer to Zeebrugge, from where it was transported to Purfleet.
During the 10-week trial, he claimed he did not know there were people in the trailer and that he watched “a wee bit of Netflix” in bed as they were loaded on.
He also said he had no idea there were migrants in two other trailers that he had dropped off at the same port in the previous 12 days.
Robinson, from County Armagh, collected the trailer when it arrived on UK shores just after midnight on 23 October.
His boss, Hughes, had messaged him: “Give them air quickly don’t let them out.”. Robinson gave a thumbs-up in reply.
But when Robinson stopped on a nearby industrial estate, he found that the migrants were all dead.
There was a series of telephone conversations between him and Hughes and Nica before Robinson eventually dialled 999.
In his evidence, Nica said Robinson told him: “I have a problem here – dead bodies in the trailer.”
On all three runs, Nica had arranged cars and a van to transport the migrants at the UK end.
Jurors were shown CCTV footage of him carrying a holdall of cash to Hughes’s room at the Ibis hotel, Thurrock, early on October 19.
Nica admitted to conspiring to assist illegal immigration in the first two runs, but he insisted that he believed the third run was all to do with smuggling cigarettes.
The day after the bodies were found, Nica travelled to Romania, claiming he was “scared” of a “big, big investigation”, but prosecutor Bill Emlyn Jones said the defendant’s version of events was “ridiculous”.