The preliminary findings of the government probe, as described by lead investigator Main Uddin Khandaker, gave the clearest explanation yet for the tragedy.
"Four huge generators were set up on each of the top floors where garment factories were located, violating rules," Khandaker, a senior home ministry official, told AFP.
"When these generators were started after a power cut they created vibration, and together with the vibration of thousands of sewing machines, they triggered the collapse," he said, adding a final probe report would be submitted after the conclusion of the recovery operation.
It also emerged today that an engineer who had warned that the building may be unsafe before it imploded on April 24 was being questioned by police after becoming the latest person to be arrested over the disaster.
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Civil engineer Abdur Razzaq Khan was detained last night after police said he had given the building the all-clear on April 23 after inspecting the cracks.
Captain Shakiur Rahman, an officer in a special army control room set up to coordinate the rescue operation, told AFP the "death toll now stands at 525".
Dozens more people are thought to have been buried alive after the eight-storey building collapsed in Savar, which lies around 30 kilometres (20 miles) to the northwest of the capital Dhaka.
Some Western fashion brands have said they are considering their future in Bangladesh and Disney has already announced it is pulling out of the country.