Belgian police are understood to be questioning a truck driver thought to have transported across Europe some the 13 refugees discovered in a lorry container in Wexford on Saturday.
Earlier, Belgian police raided a house in Brussels where as many as nine of the refugees are believed to have stayed before their ill-fated voyage.
The Garda confirmed they have been "liaising" with police forces in other jurisdictions but declined to comment on the raid by the Belgians. They have also confirmed that the eight who perished died of lack of oxygen.
The house in central Brussels was forensically examined but there were no arrests.
The truck driver is being questioned in connection with the transportation of some of the group on the final leg of their journey through mainland Europe from Cologne to Zebrugge.
It is thought the 11 - nine of whom were Turkish and two Albanians - met up with two Algerians who arrived via Spain in Zebrugge. The two children among their number died during the voyage.
A human-trafficking gang connected to a Russian-based crime ring are thought to be behind the incident. Eight of 13 died when they were discovered in a sealed lorry container in a Wexford industrial estate.
The Garda believe the refugees’ intended destination was England - a journey of a few hours - but were instead put in a sealed container bound for Waterford port.
Although it arrived in Ireland on Thursday, the container was only opened when its cargo of Italian furniture was bought to a Wexford industrial estate on Saturday, meaning the 13 endured a 53-hour journey in freezing conditions with just two tiny vents allowing air into the container.
The stowaways were discovered suffering from hypothermia and oxygen deprivation.
Post mortems carried out by the State Pathologist Prof John Harbison last night, confirmed that the cause of death was intoxication, consistent with a lack of oxygen flow to the brain.
Meanwhile, the five surviving refugees are making a steady recovery in Wexford General Hospital. Some received visits from relatives today.
A hospital spokesman said that a decision on when the five will be discharged has not been made but they will be kept in hospital for a few more days at least.