This article was reproduced with the kind permission
of the British Broadcasting Corporation
2 November 2007, 12:59 GMT
More than 60 people had to leave the megabus.com vehicle during the fire, which was believed to have started in the engine compartment at 0700 GMT.
The incident took place at Johnstonebridge - between junctions 15 and 16 - and no-one was hurt.
Thick smoke resulted in traffic being delayed for a time.
None of the 68 passengers on board the bus was hurt in the fire.
A spokesman for megabus.com, part of the Stagecoach Group, confirmed the circumstances of the incident.
We are working closely with the police and have started a full forensic
investigation to establish the cause of the fire
"A fire was discovered on the overnight megabus.com London to Aberdeen service shortly after 0700 GMT as the vehicle was travelling on the A74(M) near Dumfries," he said.
"The incident happened on the northbound carriageway between junctions 15 and 16.
"The driver followed our safety procedures and all 68 passengers on the double-decker coach were evacuated safely."
A replacement vehicle was sent from Dumfries to the scene to collect the passengers and take them on towards Aberdeen.
The company spokesman added that regular safety checks were carried out on the buses.
"This particular vehicle, which is two years old, was checked within the past three days," he said.
"We are working closely with the police and have started a full forensic investigation to establish the cause of the fire."
A Dumfries and Galloway Police spokesman said the fire had an effect on other drivers in the area.
"There was thick smoke which was reducing visibility on the motorway and traffic was delayed," he said.
"The passengers were all evacuated safely on to the hard shoulder of the motorway.
"Another bus was brought to the scene and the passengers taken on to their destinations."