GARDAI are still unable to identify the man who was decapitated by the wheels of a bus because his injuries were so horrific.
Officers investigating the case believe he may be from south Dublin, having established that he boarded a bus at Jobstown, Tallaght and headed for the city on Thursday afternoon.
But they have not yet established his identity, despite intensive checks here and overseas.
The man was crushed to death after he had been punched and then fallen from the pavement under the wheels of the bus in Dublin city centre.
Last night, detectives were questioning a 29-year-old man about the incident.
The suspect, who lives in a city-centre hostel for the homeless, was placed under surveillance by gardai yesterday morning, then arrested and taken to Pearse Street station.
The victim is known to have been involved in a verbal argument with two men minutes before he fell out in front of a double-decker bus at the junction of Nassau Street and Dawson Street. A second man, who has been identified and is living in the same hostel as the suspect, was not involved in the incident and is being treated as a witness.
Gardai say they have made substantial progress with their inquiries but are still unaware of the victim's identity.
His fingerprints have been cross-checked against garda and other police force files and his description has been circulated to gardai working in the city.
A post-mortem examination on his body was completed yesterday. It confirmed that he had died from severe head injuries, consistent with being struck by a vehicle.
The victim is in his 20s and has a number of dragon tattoos on his body.
Gardai have interviewed the badly shocked bus driver, passengers and a number of witnesses, who were walking on either Nassau Street or Dawson Street.
But they are anxious to trace other witnesses, particularly two they believe to be critical to their inquiries and who have not yet come forward.
One of the witnesses spoke with an American accent.
A forensic examination of the scene was completed yesterday while traffic was diverted from the area.
Gardai are also studying footage taken from shops, businesses and city-council CCTV cameras nearby. They have appealed to anybody with information to get in touch with Pearse Street station.
Transport Minister Leo Varadkar yesterday extended his sympathy to those affected by the incident, particularly the bus driver, and said it must have been a very traumatic and shocking experience for him.
A separate investigation into the incident is being carried out by Dublin Bus, while the company is also co-operating fully with the garda inquiries.