A large fire has engulfed part of a recycling plant, causing plumes of smoke that can be seen from miles away.
More than 50 firefighters were needed to tackle the blaze on Factory Road Sandycroft, Flintshire.
Emergency services were called at 15:15 BST on Tuesday and fire crew remained at the scene late into the night.
Motorists were warned about poor visibility on the A55 and M56 because of smoke and people living nearby were urged to keep doors and windows closed.
Factory Road was closed between Chemistry Lane and Factory Lane while the fire was tackled and, more than seven hours after the crews first arrived on scene, North Wales Fire and Rescue Service continued to urge members of the public to stay away from the area.
Earlier in the day, people living in Sandycroft were told they could lose their water supply as firefighters doused the flames.
Darren Jones, from North Wales Fire and Rescue Service, said: "Visibility is poor on the A55 and the M56 due to the think smoke coming from this incident. We are asking people travelling on those roads to reduce their speed.
"Please stay away from the riverside cycle path in Sandycroft this evening if you are cycling or walking your dog."
Euros Jones, duty tactical manager for environment body Natural Resources Wales, said: "Fires at waste sites can harm the environment, people and wildlife.
"The smoke affects the air we breathe and the water used by the fire service to fight the blaze can pollute local streams and rivers.
"In this location we are working hard to protect the Dee which is important as a source of drinking water for people in a large area, for the local economy, as a place for local people to enjoy and for wildlife.
"We have officers on site working with the fire and rescue service, advising them on the best way to reduce the effect of this fire on the environment."
Incident at Sandycroft. May affect traffic on #A494, approach with caution.— North & Mid Wales (@TrafficWalesN) May 1, 2018