Fire fighters who spent more than 12 hours tackling the blaze in Acton High Street, part of which was shut to traffic, said 'more than one seat of fire was found by the Fire Investigations Unit.
Squatters have used the derelict building as a home for 'more than 15 years, said a local man. 'It isn't the first time a fire had been started from the flats. We had one in the same block last week.
Eight fire engines were called to control the blaze which was reported at 10pm on Tuesday. It took a crew of 65 until 10am yesterday to quench the fire.
At one point cracks appeared and it was feared the building would collapse so firefighters were pulled back. Collapsing ceilings also hampered progress, said Robby Simpson, London Fire Brigade brigade assistant divisional officer.
Shirley Walter, from Acton , said it was the most exciting thing to happen there for years. 'I'm glad that building has gone, she admitted. 'It was an eyesore - it looks no different now then it did before.
A neighbour agreed. It is a good excuse to have the building demolished, he said: 'What we want is some decent clothes shops and shoe shops. We've none here in Acton.
Mrs Walter shopped at the disused Co-operative supermarket before it shut a couple of years ago. Now only pigeons and squatters the block. 'They can always find another home, she said.
It looked like they already had - leaving possessions behind. Round the back of the building was a disused garage. A pair of Hi-Tech trainers lay beside a hose-soaked matress. Two boots were waiting for their owner to return.
Also untouched was a billboard. 'We are open at night (for those of you who are still in the dark), read the poster.
It was made of plywood. 'If it had been made of metal it would have buckled under the heat, said Mr Simpson.Reuse content