Eleven people were injured when a stone staircase collapsed inside the Natural History Museum on Merrion Square in Dublin.
Two people are in a serious condition in St Vincents Hospital.
It is understood the staircase which collapsed was in a part of the building that is not normally used by members of the public.
Those injured are believed to be teachers and staff members who were involved in a training programme.
The HSE has said a number of people are being kept in hospital for further assessment, including one person who is being monitored for spinal injuries.
Emergency crews were called to the scene at around 11.30am and a fleet of ambulances took the injured to three hospitals.
Fire crews also helped to remove people from the building.
A spokesman for the Dublin Fire Service said the injured had suffered cuts and crush injuries but none of them are thought to be seriously hurt.
Traffic restrictions were in place earlier on Merrion Square and on the city routes to St Vincent's Hospital and St James's Hospital to facilitate emergency services.
The Health and Safety Authority is investigating the incident and the museum has been closed.
The Minister for Arts, Sport and Tourism, Seamus Brennan told the Dáil that the museum will remain closed to visitors for the foreseeable future.