The A45 eastbound between Stanwick and Raunds is closed after a van caught fire.
Northants Fire attended the incident at about 3.30pm today (Monday), which is believed to have involved a van containing a nitrogen cyclinder.
Highways England reports the westbound carriageway is now open, but a signed diversion remains in place for those travelling east.
Traffic is heavy in the area and East Northants Council has urged people to avoid the area.
A fire service spokesman said the fire had been made safe but a cause had not been identified yet.