No injuries have been reported after part of an office block beside Hounslow bus garage came crashing down , but witnesses have spoken of a number of near misses.
Bernard Zieja, who lives beside the office block in Aces Court, said a bus garage worker told him he had seen a man walking along London Road when the side of the empty seven-storey block collapsed.
"He said the man was walking past when it came down and was submerged in a plume of dust, but luckily he emerged unscathed.
One side of the empty Hounslow House office block collapsed at about 4.40pm today, during demolition work, sending some debris collapsing over the wall of the busy Hounslow bus station.
Police say no one is reported to have been injured, but one man told how he would have been walking right past the building when it collapsed had it happened two minutes later.
Adesh Aulakh, of North Drive, said he was in his garden when he heard a bang and initially assumed it was part of the normal demolition which began last Friday.
"It was only later when we were walking down the road that we heard neighbours talking about what had happened and came to see for ourselves," he said. "It's frightening to see what happened. What if the other side of the building had collapsed.
Mr Zieja said a smaller collapse had occurred just minutes before the second one, which caused his flat to shake.
London Road was still closed at 7pm and the bus station had been evacuated. Police said a structural engineer was due on the scene to assess the damage before the road could be reopened.
Police said the Health and Safety Executive had been informed of the collapse.
A bus garage employee said a crane appeared to have removed too much from one side of the building, leaving it unbalanced and causing the other side to crumple.