Detectives investigating the death of Henryk Piotrowski believe that four people were in some way involved with the assault on the 43-year-old.
Two are suspected of having carried out the assault, while the other two are thought to have witnessed it.
The body of Mr Piotrowski, a father of two, was discovered at 9.15am on Aug 23 at the Panda recycling centre in Walkinstown, south Dublin, after a waste lorry emptied its contents.
He somehow ended up in a commercial wheelie bin in the south inner city overnight, which was collected in the early morning.
An autopsy showed that while Mr Piotrowski suffocated inside the lorry, he had suffered injuries to his face and head that were consistent with an assault.
Detectives contacted homeless services and hostels in the city and gathered information in relation to the movements of the deceased and who he might have associated with on the street.
They also began gathering CCTV cameras at the 56 locations where bins were collected by the lorry that day. Gardaí are conducting the labour-intensive process of examining that footage in a bid to find where Mr Piotrowski was collected and any clues as to the assault.
Gardaí arrested two homeless Polish people — a man and a woman — on Wednesday and questioned them in connection with the assault. They were released without charge, pending a file to the DPP
Gardaí are not sure which of the four people — three Polish and one Czech — carried out the assault and who witnessed it.
Mr Piotrowski, whose estranged partner and two children live in Poland, was last spotted on cameras outside the Central Bank at 10.15pm on Aug 22.