Firefighters continue to contain a blaze that started on Saturday night at a recycling centre on the edge of Hemel Hempstead.
The mountain of burning wood has caused traffic disruption and water supply problems for people living nearby.
Currently all roads around the site in Appspond Lane, remain open.
The police is working with Herts Fire, Herts Highways and the Met Office to monitor the situation.
They have plans in place to promptly put in speed restrictions or close roads if needed.
The blaze has been raging since 11.45pm on Saturday and experts say it could be days before it goes out.
It has come to light that the operators of the centre were already in trouble with the Environment Agency for poor management of the site.
The agency had suspended them from importing compost or wood waste there and ordered them to remove risks of heat, fire and serious pollution.
Herts Fire Service will investigate and the Environment Agency is going to work with them and Herts County Council to decide on the next steps.