Diversions are in place to allow emergency services to deal with the crash on the A66 at Threlkeld, near Keswick.
Travelling towards west Cumbria, motorists are advised to use junction 41 of the M6, travelling along the B5305, Wigton.
Travelling towards Penrith, motorists should follow the diversions in place at the Crossthwaite roundabout, Keswick.
Cumbria Police say that the road will be closed for some time.
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The fire subsequently spread to the premises next door, resulting in over £300,000 worth of damage.
Emergency services and Cumbria County Council have been called to the incident.
Alan Wilson pleaded guilty to nine offences and was sentenced to a 225 hours Community Payback Order at Jedburgh Sheriff Court.