Officers from Environment Agency Wales are investigating after a fire broke out at a waste transfer station in Nantyglo, Blaenau Gwent, on Saturday.
A large quantity of mixed waste at the site caught fire and continued to burn over the weekend.
The site is permitted by Environment Agency Wales, and the cause of the fire is currently unknown.
The Agency will now begin its own investigation into whether the cause of the fire was related to any environmental offences at the facility.
A spokesperson from Environment Agency Wales said:
“Our main priority at the moment is to work with the Fire and Rescue Service to make sure that the fire risk has passed and that local people and the nearby environment are protected.
“Once this has happened, we will then need to look closely at what caused the fire.
“If we find evidence to suggest that the company were in breach of their environmental permit, we will take the necessary action against them.”
Agency officers visited the site numerous times throughout the weekend to monitor any environmental damage as the South Wales Fire and Rescue Service tackled the blaze.
Officers who remain at the site are reporting no signs of any impact to the nearby environment at this stage, but continue to monitor the situation closely.