New Delhi, Nov. 7 -- A wooden log supporting the concrete slab being laid on the third floor broke around 9.30am on Thursday as at least five labourers manually carried construction material in mortar pans from the ground floor to the top floor, passing them along a human chain on the staircase, according to statements given by two survivors of the Chawri Bazar building collapse.

The log's failure disturbed the balance of the other supporting wooden logs, which also gave way, causing the lintel - a horizontal concrete structural beam -- to collapse first, followed by the entire structure, said three people aware of the statements given by the survivors, Sahdev Chaudhary, 25, and Mohammad Firoz, 37. Both are undergoing treatment in the in...