One man has died, a second is fighting for life and three others are seriously injured after a 40-foot wall collapsed at a DIY store in Longford Town.
It iss understood the man who lost his life was a customer at the store and was in his late 40s.
The Health and Safety Authority has launched a major investigation into the incident which happened at the Connacht Gold DIY and Garden Centre on the Athlone road.
Up to 10 ambulances, four fire engines and gardaí from across the region rushed to the scene of the accident shortly after 2pm.
Five men were initially taken to hospital. Gardaí confirm that one has now died. He was from the local Longford area.
Another man remains in a critical condition and is being treated at the Midland Regional Hospital in Mullingar.
The other three men are in a serious condition. One is being treated in Mullingar while the other two men were taken to Tullamore.
Chief executive of Connacht Gold Aaron Forde said: "On behalf of the board, management and staff of Connacht Gold Co-op, I want to express deepest sympathy to the family of the person who was fatally injured in the accident at our Longford store today.
" Our thoughts and prayers are with them and also the other injured people.
"Safety is a primary concern for Connacht Gold and we are co-operating in every way with the emergency services, the Gardaí and the Health and Safety Authority in supporting those affected and in establishing the cause of the accident."