Eight appliances and crews and one officer were in attendance at the height of the fire.
Appliances and crews attended from:
Fire on motorway embankment, spreading to affect approximately 25 acres of field.
Firefighters are using:
- Three extended hose reels
- Water backpacks
A water shuttle has been established, and lanes one and two of the northbound carriageway is closed while the firefighters work at the scene.
Thames Valley Police and National Highways have been alerted to the incident.