A complain has been made to police amid concerns about the welfare of protected swans along the route of the A6 upgrade in Co Derry.
Campaigners claim that machinery was moved onto fields close to where hundreds of Whooper swans feed along a section of the planned route last week.
The Northern Ireland Environment Agency (NIEA) said that while there was found to be no breach of the Wildlife Order it “has initiated an investigation of any potential breach of the Environment Order” after being contacted “about a potential disturbance of swans adjacent to the A6 bypass works".
It said has not asked the contractors to cease work.
Each winter hundreds of swans fly from Iceland to feed on grassland in the area before returning north in the spring.
Campaigners say any work carried out should not cause significant disturbance to protected birds.
Environmentalist Chris Murphy last night said there “is no point in investigating this under the Environment Order as there is no provision for protecting the internationally important site”.
While work on some sections of the £160m A6 project has already started contractors have yet to begin digging near wetlands close to Lough Beg.
The new road is intended to speed up travel time between Belfast and Derry.
Earlier this month the Supreme Court in London dismissed an application by Mr Murphy to challenge the decision by the Department for Infrastructure to put the road through the area.
He has since vowed to go to the European Court of Justice.
The area was made famous by the poetry of Seamus Heaney who before his death urged authorities to use an alternative route for the planned road.
A spokeswoman for the PSNI said police received a report last week “regarding wild birds in the Hillhead Road area of Magherafelt”.
“At this time, no offence is deemed to have been committed,” she said.
