Fire crews are damping down burning waste material at a Suffolk County Council composting site at Lackford.
Suffolk Fire Service was called to the site beside the A1101 near Lackford Lakes just before 6.40am this morning.
Three appliances from Bury St Edmunds and one from Newmarket attended and are still there.
Witnesses say smoke and smell has been drifting across the nearby Lackford village.
A recycling depot at the same site was burned down several years ago.