Ancient skeletal remains have been uncovered by contractors working on the largest energy project in the country.
The unrecorded burial ground was discovered on farmland in Rush, north Dublin, as EirGrid laid piping for a high voltage direct current underground power line.
Several skulls and bones were recovered on the strip of land near Rogerstown estuary, which locals historians believe could date back to the Vikings in the 9th century.
An on-site archaeologist has informed the National Monuments Service and is expected to be given the go-ahead to carry out a full archaeological survey next week.
It is not yet known how many bodies are buried there or exactly what era they date back to.
A spokeswoman for EirGrid said the section of land has been cordoned off and was being protected from heavy rainfall until examinations can be completed.
However work is continuing in the surrounding area.
"A previously unrecorded burial ground has been located on private land in Rush earlier this week," she said.
"It wasn’t marked up on any ordnance survey maps."
She said there was no evidence of disturbance on the land before the 1.5 metres deep trench was dug on the farmland.
It is believed to be close to the former port of Lusk which was used by the Vikings.
Local historian Kevin Thorp said how the remains were buried would be the key to identifying how long they have been there.
"It sounds like a Viking settlement where people were buried," he said.
"But it all depends on whether the bodies were criss crossed or buried in straight lines, if there was any clothing on them, the composition and if they were men or women or young and old."
Mr Thorpe, of Loughshinny and Rush Historical Society, said the final resting place of hundreds of people who perished when the Tayleur was shipwrecked off Lambay Island in 1854 also remains unknown.
"Altogether more than 300 people went down with that ship, mostly women and children," he added.
The €600 million east-west interconnector will link Ireland's and Britain's national grid with an underwater pipeline from Wales to Rush.
PA