The A380 is blocked and motorists are being advised to avoid the area after car burst into flames on Telegraph Hill.
Both police and the fire brigade attended the emergency, which was reported at around 4pm today.
There are no reports of any casualties, although smoke and debris is scattered across the road.
The A380 southbound towards Torquay remains closed, with queues reported back to the junction with the A30 and the M5.
Heavy traffic is being reported in the area.
Traffic-reporting service Inrix says: “A380 Telegraph Hill Southbound closed, queueing traffic for seven miles due to vehicle fire between A38 (Splatford Split, Kennford ) and B3192 ( Ashcombe / Teignmouth turn off, Ashcombe ).
“Congestion to the M5, back to J30. The road has been closed after a vehicle caught fire in a layby. Affecting traffic heading towards Newton Abbot.”
Police are strongly advising people to avoid the area.
A Devon and Cornwall Police spokesperson said: “We are urging people to avoid the area.
“We had a call at around 4pm to reports of a car on fire.
“There is smoke and debris across the carriageway so please avoid it.
“The fire brigade is on the scene and we also have someone there.”
At least one fire engine remains on the scene.
“Two fire engines were in attendance after reports of a vehicle fire on Telegraph Hill,” said a fire control spokesperon.
“The police are also in attendance.”