GARDAÍ are following a "definite line of inquiry" after up to 30 tonnes of waste was dumped illegally near the border.
A lorry believed to have been used to transport the rubbish to the secluded location has been seized.
Officers came on the scene as the waste being dumped on Saturday night.
It included builders' rubbish and household waste, estimated to be between 25 to 30 tonnes.
The lorry has been taken to a secure location for a technical examination.
It was reported that the alleged driver fled across nearby fields. There have been no arrests but gardaí said officers were following a definite line of inquiry.
The lane, off the Doyle's Fort Road, Dundalk, has now been sealed off by Louth County Council.
Garda Superintendent Gerry Curley of Dundalk Garda Station said an investigation had begun.
"We are working on identifying who is responsible," he said.
