A 40-year-old man has appeared at Dublin's High Court in connection with the manslaughter of 39 Vietnamese nationals.
The bodies were found in a lorry trailer in Grays, Essex, in October 2019 after it landed at Purfleet from the Belgian port of Zeebrugge.
Ronan Hughes, of Leitrim, Silverstream, Tyholland, County Monaghan, was in court for the short hearing.
Essex Police is seeking his extradition.
The court heard that he was arrested on Monday at his home and that if he is extradited he will face 39 manslaughter charges and one of conspiracy to assist unlawful immigration.
At the hearing, Belfast-born Mr Justice Paul Burns informed Mr Hughes of his rights.
The judge remanded him in custody until 1 May 2020.
Mr Justice Burns said he would seek more information about Ronan Hughes' alleged involvement in the offences.
The judge also indicated that he would be prepared to hear a bail application on 29 April 2020.
On 8 April, 25-year-old Maurice Robinson, of Craigavon, County Armagh, pleaded guilty at the Old Bailey to 39 counts of manslaughter.
He had previously pleaded guilty to conspiracy to assist unlawful immigration.
Robinson will be sentenced at a later date.
Four other men will stand trial at the Old Bailey in connection with this investigation on 5 October.
Eamonn Harrison, 22, of Mayobridge, Northern Ireland, who under a European Arrest Warrant faced 39 charges of manslaughter, has been granted leave to appeal against his extradition to the UK.
He also faced a charge of conspiracy to traffic people, as well as conspiracy to assist unlawful immigration.
A further hearing will be held in Dublin on 7 May.