A Polish man, who was attacked while walking to work in the early hours of Saturday, died last night in hospital.
Victim Lukasz Rzeszutko (27) had been on a life-support machine at Beaumont hospital in Dublin before he died.
The garda investigation into his death has now been upgraded to a murder inquiry.
A post-mortem examination is expected to be held today.
Mr Rzeszutko, who is from Olsztyn in Poland and had been living with his partner in Clarehall, on the northside of Dublin, suffered severe head injuries in the unprovoked attack.
He also received several injuries to his body after he was set upon by a group of young men, who kicked and punched him.
Gardai said he appeared to have been the victim of a random assault although robbery might have been the initial motivation.
The incident took place between 4am and 5am at the Newtown industrial estate, off the Malahide Road.
He was walking to work at Kish Fish seafood processing plant for a 5am start to his shift when he was attacked.
He was discovered lying on the ground by another early morning worker around 5am and the emergency services were immediately alerted.
Mr Rzeszutko was taken to hospital in a critical condition and his parents later arrived from Poland to be at his bedside. A brother and some of his friends already work here.
Last night two teenagers were being questioned.
One of the teenagers was arrested by gardai on Sunday afternoon and taken to Raheny station for questioning.
The second teenager was detained later under the same legislation and brought to Clontarf for questioning.
Their periods of detention were extended by a senior officer yesterday.
Gardai said last night they had interviewed a large number of people in connection with their inquiries and believed that those involved were originally from the area.
One investigator said: "Mr Rzeszutko was an innocent man, who had come here from Poland to find work.
"He was minding his own business while walking to his job in the early hours of the morning when he was suddenly attacked."
Mr Rzeszutko was described last night as "exceptional" and well-respected by management at the fish company where he worked.
His parents are being assisted by the Polish Embassy in Dublin.
His shocked colleagues did not want to speak publicly yesterday but, in a statement, Kish Fish said Mr Rzeszutko had been working with the company since 2007.
"We are all shocked and devastated by this brutal assault. Lukasz is an exceptional colleague -- he is both popular and well-respected by everyone in Kish Fish.
"Our thoughts and prayers are with Lukasz and his family, here in Ireland and in Poland," the statement added.
Local businesses in the industrial estate where the attack took place expressed their devastation yesterday.
Mark Jenkins, co-owner of car parts shop Summerhill Spares, which is located next door to the fish plant, said he first found out about the assault as he opened up at 7.45am on Saturday.
"There was crime scene tape up everywhere and we had to work from the side entrance to the building," he said.
"It was really a shock to see.
"Our business has been here five years, and this is the first incident like this that we've come across."
Artane and Whitehall Sinn Fein councillor Larry O'Toole said the event was "a really sickening situation".
"From talking to neighbours and locals I know people are very upset here about the whole thing."