Members of a million-pound people-smuggling ring could be facing life behind bars for the manslaughter of 39 migrants.

The Vietnamese migrants, aged between 15 and 44, were found dead in the back of a trailer in Essex on October 23 last year.

They had suffocated in sweltering temperatures as the airtight container was shipped from Zeebrugge to Purfleet.

The “unscrupulous” gang behind the illegal shipment were motivated by greed as they pursued profits of more than £1m that month alone.

Following a 10-week trial, Romanian ringleader Gheorghe Nica, 43, from Basildon, and lorry driver Eamonn Harrison, 24, from County Down, were found guilty on Monday of 39 counts of manslaughter.

They were also convicted of their part in the people-smuggling operation with lorry driver Christopher Kennedy, 24, from County Armagh, and Valentin Calota, 38, from Birmingham.

The verdicts bring the total number of people convicted in Britain to eight, including haulier boss Ronan Hughes, 41, of Armagh, and 26-year-old lorry driver Maurice Robinson, of Craigavon, who admitted manslaughter.

Prosecutors are considering charges against a further three people. The maximum sentence for people-smuggling is 14 years in prison with manslaughter carrying a possible life sentence.

Detective Chief Inspector Daniel Stoten, of Essex Police, said the gang were “greedy” but “complacent”.

He said: “You would not transport animals in that way but they were quite happy to do that and put them at significant risk.”

The Old Bailey heard how the gang offered a “VIP” service to Vietnamese migrants, who gathered in Belgium and France.

They charged about £13,000 a head to transport migrants in a trailer via the Channel Tunnel or by boat to Essex.

The network, led by Nica and and Hughes, had been operating for at least 18 months, despite repeatedly coming to the attention of authorities.

On the morning of October 22, Harrison picked up 39 migrants from Bierne in France.

His trailer was loaded on to the Clementine ship which departed from Zeebrugge at about 4pm, docking at Purfleet shortly after midnight.

Robinson, who collected the trailer at 1.08am, was instructed by Hughes via Snapchat to “give them air quickly don’t let them out”.

When he opened the doors, a plume of vapour escaped and Robinson stands for 90 seconds before getting back in the cab.

In the 23 minutes before he dialled 999, Robinson exchanged panicked calls with his boss Hughes and Nica, who had been waiting for him in Orsett with his drivers.

The first police officer on the scene described finding half-naked bodies “closely packed” together lying in the trailer, some “frothing at the mouth”.

Mobile phones recovered from the victims showed how they had tried to raise the alarm and left goodbye messages for loved ones as they ran out of air.

Others had used a metal pole to try to punch a hole through the roof or attract attention, the court heard.

Kennedy, Harrison and Calota, who picked up migrants at Orsett on October 18, variously claimed they had thought they were transporting cigarettes, alcohol and stolen lorry parts.

Nica admitted being roped in by convicted cigarette smuggler Hughes for earlier runs, but said he thought Robinson had a load of cigarettes when he showed him where he could unload in Orsett the night before the tragedy.

But prosecutor Bill Emlyn Jones told jurors the operation required “meticulous” planning and each defendant had to be “in the know”.

The victims were: Dinh Dinh Binh, 15, Nguyen Minh Quang, 20, Nguyen Huy Phong, 35, Le Van Ha, 30, Nguyen Van Hiep, 24, Bui Phan Thang, 37, Nguyen Van Hung, 33, Nguyen Huy Hung, 15, Nguyen Tien Dung, 33, Pham Thi Tra My, 26, Tran Khanh Tho, 18, Nguyen Van Nhan, 33, Vo Ngoc Nam, 28, Vo Van Linh, 25, Nguyen Ba Vu Hung, 34, Vo Nhan Du, 19.

Tran Hai Loc, 35, Tran Manh Hung, 37, Nguyen Thi Van, 35, Bui Thi Nhung, 19, Hoang Van Tiep, 18, Tran Thi Ngoc, 19, Phan Thi Thanh, 41, Tran Thi Tho, 21, Duong Minh Tuan, 27, Pham Thi Ngoc Oanh, 28, Tran Thi Mai Nhung, 18, Le Trong Thanh, 44, Nguyen Ngoc Ha, 32, Hoang Van Hoi, 24, Tran Ngoc Hieu, 17, Cao Tien Dung, 37, Dinh Dinh Thai Quyen, 18, Dong Huu Tuyen, 22, Nguyen Dinh Luong, 20, Cao Huy Thanh, 37, Nguyen Trong Thai, 26, Nguyen Tho Tuan, 25, and Nguyen Dinh Tu, 26.