Lorry driver Maurice Robinson has admitted the manslaughter of 39 people who were found dead in a refrigerated trailer in Essex.
The 25-year-old from Northern Ireland pleaded guilty at the Old Bailey on Wednesday.
Robinson, who is known as Mo, was arrested shortly after the bodies were discovered in the back of his lorry on an industrial estate in Grays last year.
The bodies of the Vietnamese nationals were discovered by emergency services shortly after the lorry arrived on a ferry from Zeebrugge in Belgium in the early hours of October 23.
Among the men, women and children were 10 teenagers, two of them 15-year-old boys.
Robinson, of Craigavon, County Armagh, and four others appeared at the Old Bailey via video-link.
During the hearing, he admitted 39 counts of manslaughter on or before October 24 last year. He denied a further charge of transferring criminal property.
He had previously pleaded guilty to conspiracy to assist unlawful immigration and acquiring criminal property.
British Romanian Gheorghe Nica, 43, of Mimosa Close in Langdon Hills, denied 39 counts of manslaughter.
He also denied one count of conspiracy to assist unlawful immigration between May 1 2018 and October 24 2019.
Romanian national Alexandru-Ovidiu Hanga, 27, of Hobart Road in Tilbury, denied a charge of conspiracy to assist unlawful immigration.
Christopher Kennedy, 23, of Corkley Road in Darkley, Co Armagh, Northern Ireland, has previously denied conspiracy to assist unlawful immigration
Valentin Calota, 37, of Cossington Road in Birmingham, was not asked to enter a plea to the charge of conspiring to assist unlawful immigration.
Prosecutor William Emlyn Jones QC said a human trafficking conspiracy charge was being dropped in relation to Kennedy and Robinson.
He asked for three weeks to decide whether to proceed with a trial against Robinson on the outstanding charge he faces.
The other defendants face a trial at the Old Bailey lasting up to eight weeks from October 5.
Additional reporting by PA Media