The Health and Safety Authority (HSA) is conducting an investigation into a fatal accident at a site on the western bypass near Dundalk, Co Louth, yesterday.
A 24-year-old man was killed and two others were injured in the accident which occurred shortly before 1.30 p.m.
It happened on a site in the Gibstown area of Dundalk, at the end of the M1 motorway.
It is understood a concrete beam was being lifted into place across the new section of motorway when temporary supports collapsed.
The young man, whose name has not yet been released, was underneath.
He was taken to Louth County Hospital in Dundalk, where he was pronounced dead on arrival.
The two other workers who sustained injuries were taken to Our Lady of Lourdes Hospital in Drogheda. They were in a stable condition last night.
The site was closed and preserved for technical examination by the HSA, which arrived in the afternoon.
A HSA spokesman said: "We are investigating a fatal accident at Dundalk. Inspectors are on site and will remain for as long as the investigation requires."
Gardaí at Blackrock station in Dundalk are also investigating the accident.