The cause of the massive fire which destroyed buildings in Edinburgh's historic Old Town may never be known, experts are expected to concede.

It is anticipated that officials will say that they will never know for certain what started last month's blaze, which caused damage running into millions of pounds.

The destruction caused by the fire and by the emergency demolition work that followed has frustrated fire investigators attempting to pinpoint the cause of the blaze.

The fire, which was the most serious and spectacular in Edinburgh for years, is believed to have started close to La Belle Angele nightclub in the Cowgate.

Fire damaged buildings had to be demolished

It destroyed more than a dozen properties in linked premises up to seven storeys high, including the world-famous Gilded Balloon comedy club.

The ferocity of the fire meant that what remained of most of the buildings was too unstable for inquiry teams to carry out immediate, detailed investigations.

Subsequent collapses and safety-related dismantling have also hindered the quest for clues.

After a meeting of representatives of interested organisations, ranging from the fire brigade to insurance companies, it is expected to be announced that the reason for the outbreak will remain unknown.

One senior investigator believes there are two or three probable causes, but "thinking and proving are two different things".

Police are waiting for the fire brigade's final conclusions before sending a report to the procurator fiscal.

The cause of the blaze is not thought to be suspicious.

Top comics including Phil Jupitus, Eddie Izzard, Jo Brand and Ross Noble turned out for a benefit gig for the Gilded Ballloon on Sunday evening.

Stars who took part in the event in London's Piccadilly Theatre paid tribute to the part the venue had played in launching their careers.