Fifteen fire crews are tackling a large building blaze near the A1M this lunchtime (Saturday).
Firefighters are at Old North Road, Sawtry, near the Greenfields pitches.
It is believed the fire is at East Anglian Galvanizing Ltd.
Smoke can be seen from a large distance.
Cambridgeshire police said it has closed the B1043/Old North Road between the junctions of St Andrews Way and the A1M southbound to enable fire crews to tackle the blaze.
Cambridgeshire Fire and Rescue Service said crews from Cambridgeshire, Lincolnshire and Northamptonshire are at the scene after being called to the blaze at 11.41am.
A spokeswoman said residents are being advised to keep their doors and windows closed.
Police and the ambulance service are also at the scene.
No further information is currently available.