The fire service are tackling the lorry fire on the A170 Sutton Bank Road, above the A19.
Update 4.35pm: The smoke has cleared from the A19 more quickly than expected and NYCC Highways officials and the fire service have deemed the carriageway safe.
The A19 has now reopened in both directions.
Background Information About The Fire
Officers were alerted at around 9.45am today (21st August 2012) after reports that a load of hay bales had caught fire on the back of a wagon on the A170.
The vehicle is on fire on a bridge over the A19 and flaming debris is falling onto the carriageway below.
As a result the A19 was closed in both directions as emergency services deal with the fire.
Traffic was diverted through Thirsk.
The driver of the vehicle was not injured in the incident.