Work on a section of the LNG gas pipeline project in Pembrokeshire has been temporarily halted by archaeologists.
The pipeline will span the breadth of south Wales
They are examining a site at St Botolphs near Milford Haven, although have not revealed what they have found.
Contractors have been moved to work on other parts of the route, which will run the breadth of Wales.
A spokeswoman for the National Grid said it should be known in the next few days if the discovery was significant.
She said work was stopped last week and the site was still being investigated.
"We have archaeologists monitoring wherever we are using digging equipment," she added.
"We have suspended work, as we have done on a number of other occasions, so they can continue their excavations.
"We are still at the stage of is it or isn't it anything of significance.
"In a few more days we should know more."
The natural gas pipeline will link two liquefied natural gas (LNG) terminals at Milford with the UK's gas supply.
Earlier this year work was stopped on a section of the route at St Clears after a human thigh bone and other fragments were uneathed by contractors.
The remains were later identified as specimens used by the medical profession or students, likely to have been dumped many years ago with other rubbish at the site.