Minister for the Environment Dick Roche has ordered Waterford City Council to protect a Viking site at Woodstown, Co Waterford.
The Woodstown site, which was discovered in 2003, is on the route of the proposed Waterford City by-pass, the N25.
The discovery was an unexpected find and is considered to be of historical significance.
"It is a multi-period site with extensive Viking occupation and is considered a National Monument within the meaning of the National Monuments Acts," Mr Roche said.
The minister will establish a working group, including representatives of the Department and the National Museum, to advise on the long-term strategy to deal with this site.
Meanwhile, the National Roads Authority has indicated that it is in favour of a modification to the alignment of the road which would avoid the site.