The mother of one of the five teenagers killed in a devastating motorway crash has spoken out, offering an apology to the family of three sisters who were seriously injured in the same collision.

Margaret Berry, whose 18-year-old son Jeremy O'Brien died in the crash on the M9 near Moone, Co Kildare, told The Sun she wished her son had never got into the car. "My heart goes out to this poor family and if I could see them I would apologise," she said. "This tragedy should never have happened. I am not proud of what happened and I don't condone what they did."

Berry, who said she raised her son on her own, described the loss as losing "a part of my life". She said her son was "not some kind of prolific criminal or car thief", adding that he "never took drugs or drank" and was "well known across Ireland and the UK". She also said people should not wish harm on the boys, saying "they aren't paedophiles or rapists".

The crash, which occurred in the early hours of Sunday, 16 August, involved a BMW travelling the wrong way on the motorway and a Hyundai carrying the three sisters — Niamh and Alma Kinsella, both in their 30s, and younger sister Ella Hendricken, in her 20s — along with Alma's seven-year-old son Yemi. The sisters suffered what have been described as "catastrophic" injuries and remain in hospital. One sister has spinal injuries and several broken bones, though the family has moved from critical to seriously injured. Yemi broke his leg and asked for his cast to be painted red because he supports Manchester United.

The family were on their way to Dublin Airport for a holiday, with reports saying they were travelling to the UK for a family wedding. A GoFundMe page set up by Bryan Curley, a friend of the sisters, has raised more than €700,000. Curley said the priority is "giving Ella, Niamh, Alma and those closest to them the privacy and space they need".

A vigil was held at St Clare's Church in Graiguecullen, Co Carlow, for the four family members injured in the crash. Bishop Denis Nulty said the community felt "shock" as well as "maybe fear and grief". He said: "The thing about it is, they could be any one of us on the road from Carlow to catch an early morning flight from Dublin Airport." He also thanked first responders and said: "We also remember the five boys in the [other] car and that's the Christian thing to do." Father John Dunphy said the hearts of the community had been "numb" since Sunday morning, but added: "We prayed that they will recover. We knew it would be a long road back. Thankfully, they're on that road and please God, they will make a full recovery."

The five teenagers who died were Jeremy O'Brien, 18, Alex McCarthy, 17, Joey Carthy, 15, Jack Kennedy, 17, and Kamil Pustkowski, 17. Funerals for Alex McCarthy, Joey Carthy and Kamil Pustkowski were held on Friday. Jeremy O'Brien's funeral took place on Monday at The Holy Family Church in Askea, Carlow, with a lone bagpiper and horse-drawn hearse leading the procession. He was buried in St. Mary's Cemetery. Jack Kennedy's funeral is set to take place on Tuesday at St Michael's Parish Church in Athy.

Gardai have confirmed a heavy presence at the funerals over fears of stunt driving processions or public order incidents. Armed detectives and Public Order Units were stationed at checkpoints around Carlow town and roads leading to the church.

At Jeremy O'Brien's funeral, Father Tom Little said in his homily: "what the boys did was wrong", but that "tragedy" must not become the whole story. He added: "The death of a young person is always difficult to accept" and "Families have been changed forever."

The Garda investigation into the crash is ongoing. Detectives are examining CCTV and have urged witnesses to come forward. Reports indicate gardai had received reports of the boys attempting to break into homes and cars earlier that night, and that a patrol car requested the BMW to stop at around 2am, but it sped away and drove the wrong way. Gardai did not follow the car onto the motorway due to the risk of a head-on collision. The BMW is believed to have been travelling at speeds exceeding 120km/h when it struck the Hyundai head-on. The family in the Hyundai were travelling on the correct side of the motorway.