A dust cloud which leaked from a Hanson Cement works is being investigated by the Environment Agency.
The leak from the former Castle Cement plant at Padeswood was reported by residents in Penyffordd, near Mold last week, when they found their cars covered in what at first appeared to be frost.
Environment Agency Wales said it had taken almost 30 calls from the public.
“We are conducting our own detailed investigation on site and in the surrounding area of Penyffordd and Penymyndd to assess the impacts of this incident,” a spokesman said.
“If we discover that there have been any breaches of their environmental permit, we will take appropriate enforcement action against the company.”
The company has arranged for villagers affected by the dust cloud to have their cars cleaned.
A spokesman for Hanson said a problem had occurred during the cement milling process on Wednesday evening and this had resulted in cement dust escaping from a storage silo. The process was shut down immediately and the company is now investigating the cause.
“We have been assured that there is no threat to health. It’s a nuisance problem rather than a health issue.”