The accident, involving an HGV and two other lorries on the A74 between Carlisle and Gretna caused traffic chaos on the M6.

A single southbound carriageway of the A74 was due to reopen at 10pm, but the northbound carriage will remain closed.

The father and son are believed to come from Manchester.

Police are advising people not to travel on the road, which links England and Scotland, and recommended that anyone working in Carlisle who wanted to return to Scotland or Longtown should seek temporary accommodation.

Cumbria Police said traffic was gridlocked, with the A74 at Metal Bridge and a section of the M6 closed for much of Wednesday as recovery work continued.

Officers injured

Two police officers were also taken to hospital after coming into contact with powdered dye at the scene of the crash.

The paint dye leaked from one of the crashed lorries, but police stress it is not thought to be harmful to people in their cars.

Officers without protective masks were temporarily withdrawn from the scene as a precaution.

The accident happened at 0400 GMT in an area known locally as the Cumberland Gap.

High winds

Cumbria Police said both lanes of the A74, which links the M74 and the M6, were closed from Gretna services to junction 44.

Northbound traffic was also being diverted on to the A7 at Longtown.

A spokesman for Cumbria Police said: "We believe a lorry travelling south overturned in high winds and crossed the carriageway colliding with two other vehicles.

"The recovery operation is being restricted because the A74 only has two lanes and no hard shoulder so gaining access is difficult.

"The situation is also being made more difficult because one of the lorries was carrying a powder dye used in the paint industry which is not hazardous, but can cause coughs if exposure is prolonged."

People are being advised to avoid the area completely unless they have urgent business.