The Archbishop of San Francisco has dedicated a special mass in the city's cathedral to the six students killed in Berkeley last Monday.
Around 1,000 people attended the special mass, with many wearing GAA jerseys and Irish soccer and rugby jerseys.
Archbishop Salvatore Cordileone said the people of San Francisco stood in solidarity with the people of Ireland at a time of "inexplicable suffering".
He invited two Irish priests to concelebrate with him; Pastor of St Columba Church in Oakland Fr Aidan McAleenan - where the bodies of four of the students had been reunited with their families, and Fr Brendan McBride of the Irish Immigration Pastoral Center.
Delivering the homily, Fr McBride questioned what could be said about such a terrible occurrence, adding that his heart was broken for those involved.
He asked for strength as "our work has just begun" now bringing the students home to Ireland.
Earlier, the bodies of four students who died in the balcony collapse arrived back to Ireland on the same flight as their relatives.
The families of Eoghan Culligan, Lorcán Miller, Niccolai Schuster and Eimear Walsh were on board Aer Lingus flight 146 from San Francisco, which touched down at around 11.10am.
The hearses carrying the remains of Eoghan, Lorcán and Eimear left the airport together.
Niccolai's family took some additional time together before they left the airport with his remains.
RTÉ's Laura Fletcher reports from Dublin Airport as the bodies of four Berkeley victims arrive home https://t.co/3QOqaY5vZi
— RTÉ News (@rtenews) June 21, 2015
Olivia Burke's family will return to Ireland with her remains tomorrow.
Funerals in Ireland for the students who died in the tragedy will begin on Tuesday.
The funeral mass for Eoghan Culligan will take place in the Church of the Annunciation in Rathfarnham in Dublin at 11am on Tuesday.
Also on Tuesday, Eimear Walsh's funeral mass will take place at 11am in the Church of Our Lady of Perpetual Succour in Foxrock in Dublin.
At 11am on Wednesday a funeral mass for Niccolai Schuster will take place in the Church of the Three Patrons in Rathgar in Dublin.
A funeral mass for Olivia Burke will take place at 11am on Wednesday in the Church of Our lady of Perpetual Succour in Foxrock in Dublin.
The body of Ashley Donohoe will remain at a funeral home in Sonoma until her family returns from Ireland from Olivia's Irish service.
She will then be cremated.
Details for Lorcán’s funeral mass have not yet been released.
The families have asked for privacy so that they can mourn the sudden and tragic deaths of their loved ones with the dignity they deserved.
Last night, four of the families issued a statement thanking everyone, in the United States and Ireland, for their sympathy and support.
They described the sympathy and support they had received as a tremendous comfort, thanking local authorities, emergency services, medical staff, the Irish Consul, the parishes and communities of Berkeley and others.
In particular they said they wanted to thank the other students who were in the apartment and the wider complex that night.
They said that the manner and speed at which they reached out to the families... and to each other was "faultless" and said that their children were "extraordinarily blessed in their friends".
Earlier, a joint funeral mass for two of the victims cousins Olivia Burke and Ashley Donohoe, was held in California
Speaking through a family friend after the funeral, the parents of Olivia Burke and Ashley Donohoe said their daughters and all of those who were at the party that night were responsible young adults who felt they were in a safe environment, but the party turned tragic through no fault of their own.
The parents of Olivia Burke and Ashley Donohoe issued a statement after the funeral mass for the two students https://t.co/a6qw9eOca2
— RTÉ News (@rtenews) June 20, 2015
They said both girls were intelligent and talented and that Ashley would have liked to make a difference in the world.
In her memory they asked people to donate to Cystic Fibrosis Ireland in lieu of flowers or other donations.
Friends of Ms Burke spoke of their memories of the 21-year-old during a celebration of life ceremony in Sanoma California last night.
Ms Donohoe's sister, Amanda, said the girls had lived their lives to the full and would never be forgotten.
Amanda Donohoe whose sister Ashley died in the Berkeley balcony collapse paid tribute to her and her cousin Olivia. https://t.co/yqN3GO4m2A
— RTÉ News (@rtenews) June 21, 2015
Last night The Script dedicated a song to the families of the six students who died in Berkeley at their sold-out concert in Croke Park.
Lead singer Danny O'Donoghue went to St Mary's College, where two of the students who died (Eoghan Culligan and Niccolai Schuster) also went to school.
The Script dedicated a song to the families of the six students who died in Berkeley at their concert in Croke Park https://t.co/XdB85mMHas
— RTÉ News (@rtenews) June 20, 2015
Vocalist and guitarist Mark Sheehan told the crowd "Ireland lost six of its sons and daughters during the week in California to a terrible tragedy."
Though he said it "wasn't a lot", he dedicated "If you can see me now" to the students’ families, saying it was a song they wrote about their own grievances.