Investigators from the police and fire brigade are sifting through the debris which was left after Saturday night's blaze.

Contractors are preparing to start demolishing historic buildings ravaged by the city's worst blaze in living memory.

After a fire of this severity some of the evidence that we would normally be looking for will have been destroyed Ken McKim Fire investigator

Investigators have now been given access to the badly damaged properties in the Cowgate.

A spokesman for the emergency services said there was no indication at this stage as to what had caused the blaze.

Lothian and Borders Fire Brigade Investigator Ken McKim said: "It is going to be important for us to work with demolition crews to make sure that we get clear access to the areas that we need to investigate.

"Clearly after a fire of this severity some of the evidence that we would normally be looking for will have been destroyed.

"But we are confident that we can get a good investigation here."

Inspecting buildings

Demolition plans are ready and work is scheduled to start on site on Wednesday.

Experts hope that some stonework can either be saved or reproduced when the area is redeveloped.

Officials and engineers have been inspecting the buildings in the affected area, which includes Hastie's Close, Chambers Street and South Bridge.

The cause is yet to be established

Photographers are starting the process of making a record of what is left of the site.

More than 150 people were evacuated during the outbreak in the fashionable club district on Saturday evening.

It caused damage estimated at tens of millions of pounds.

About 13 buildings in the World Heritage site were destroyed, including the world-famous Gilded Balloon comedy club.

City council leader Donald Anderson said the fire had "left a gaping wound in the heart of the city".

This could be an extremely useful source of funding to help repair and restore as much damage in the Old Town as possible Kevin Pringle SNP election candidate

The Scottish National Party is urging the Scottish Executive and the local authority to apply for emergency assistance from the World Heritage Fund.

The SNP's Holyrood election candidate in Edinburgh Central, Kevin Pringle, said money was available for World Heritage Sites which have been damaged by fire.

"This could be an extremely useful source of funding to help repair and restore as much damage in the Old Town as possible," he said.

"If you don't ask, you don't get - and First Minister Jack McConnell should be prepared to put the authority of his office behind an application for Edinburgh.

Equipment destroyed

"Possible EU assistance should also be investigated."

Firefighters were still tackling burning pockets in the buildings 48 hours after the blaze broke out.

The fire spread to the University of Edinburgh's School of Informatics building, where research work and equipment was destroyed.

Computer equipment worth thousands of pounds and rare documents detailing the history of the subject were lost.