A fire at a recycling plant in West Dereham is being treated as arson, police have confirmed.
Emergency services were called to Glazewing in Station Road at around 3.30am on Monday to reports of 500 tonnes of mixed municipal waste alight.
Residents of the village were advised to keep their windows and doors shut while the fire was dealt with throughout the day.
Three crews remained on scene during the day to monitor the situation, while a team of representatives from West Norfolk Council, Glazewing and the Environment Agency held a multi-agency meeting.
Air quality assessments were also being carried out by West Norfolk Council officers.
Firefighters left the scene at about 4.30am on Tuesday, just over 24 hours since they responded to reports of the incident.
An investigation is ongoing.