The public has been urged to help bring those responsible for burning illegal materials on eleventh night bonfires before the courts.
Anne Blacker, of the DoE, said a difficulty in persuading witnesses to come forward made it hard to bring prosecutions.
On Wednesday, concerns were raised about a large bonfire in Antrim which contains hundreds of rubber tyres.
Ms Blacker said the situation had "caused a lot of frustration".
Residents in the Ballycraigy area of Antrim, where the bonfire has been built, have said that apart from damage to the environment, they fear the toxic fumes given off by the fire could damage their health.
SDLP assembly member for South Antrim Tommy Burns said more should be done to protect the public.
"There are thousands of tyres and thousands of pallets in the Ballycraigy bonfire and in a few hours it will be poisoning people over a huge area," he said.
"This is not about culture, it is about law-breaking."
A spokesman for the Department of Environment said that despite illegal materials being burned on the bonfire, it would not be extinguished unless it became an issue of public safety.
Antrim Ulster Unionist councillor Drew Ritchie, head of the town's bonfire committee, said they would work to ensure next year's fire would be tyre-free.