CIE has ordered a full internal investigation into the bus accident at Wellington Quay yesterday, which killed five people and injured 12.
After a meeting at the crash scene with transport minister Seamus Brennan, CIE chairman John Lynch said he would proceed immediately with the investigation into the worst accident in Dublin Bus history, while gardaí are also investigating.
Both investigations will seek to explain how an Airlink Express bus mounted the footpath outside the Clarence Hotel and cut inside a stationary Dublin bus ? ploughing into the large crowd of people standing on the footpath queueing to board the No 66 bus service to Maynooth.
The incident happened at around 1.20pm yesterday, when both lanes of the South Quays were busy with traffic.
Three of those killed were women and two were men, while at least one of the dead was a non-national.
It is understood that most of the dead were killed instantly, but at least one person died later at the scene.
A number of people were trapped under the bus and were seriously injured.
Emergency workers were quickly on the scene, with seven fire engines attending from the Tara Street and Phibsborough stations.
Gardaí closed off the South Quay area from Aston Quay to Wood Quay as mounted gardaí and members of the traffic unit from Dublin Castle held back onlookers.
Airbags, with a capacity to lift 36 tonnes, were used to lift the front and centre base of the bus to enable ambulance crew to drag them free.
Fire crew members later told reporters that the injuries they witnessed were the most horrific they had ever seen.
The Taoiseach, Bertie Ahern, visited the scene and talked with emergency workers and gardaí.
He expressed his sympathies for the families of the dead and injured. He said the accident was one of the most horrific he had seen.
"It was with great sadness and distress that I learned about those that have lost their lives and the many others who have been injured, going about their daily lives in Dublin city centre today, " the Taoiseach said.
The injured were later removed to St James' Hospital, St Vincent's Hospital and the Mater Hospital. Five of these people's injuries were serious but not immediately life threatening.
A spokesman for Dublin Bus said yesterday's accident was unprecedented in terms of multi-fatalities involving buses from the Dublin bus fleet.
The accident brings the number of people killed in road traffic accidents so far this year to 52, 15 more than the same period last year.