Firefighters have left the scene of a blaze at a waste management centre in West Dereham, near Downham Market.
Crews were at Glazewing Ltd in Station Road until about 4.30am today, a spokesman for Norfolk Fire and Rescue Service said.
They were first called to the centre at about 3.30am yesterday.
The fire was in a stockpile of about 500 tonnes of mixed municipal waste.
In a multi-agencies statement, the Environment Agency, Norfolk Fire Service and West Norfolk Council, said yesterday that air quality assessments had been carried out, and drainage from the site had been blocked to prevent contaminated water entering the local watercourses.
The causes of the fire are under investigation.
Earlier in the day, a warning was issued to people in the area to keep windows shut, as toxic fumes may have been in the air.
The same site was engulfed in flames in August last year.
On that occasion, 13 fire engines and specialist appliances from across East Anglia were called to the blaze. The fire blazed for several days before the wastepile was completely moved, quenched and relocated to storage bays or skips on site.
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