Bangladeshi police have arrested the engineer who warned that a building housing garment factories was unsafe a day before it collapsed.
Police official Ohiduzzaman said Abdur Razzak Khan worked as the Rana Plaza owner's consultant when the owner illegally added three floors to his five-story building.
Khan was arrested on Friday on a charge of negligence.
He appeared on television after inspecting the building on April 23 and said it was unsafe.
Police ordered it evacuated, but the order was ignored and it collapsed the next day.
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The death toll from last week's collapse of a garment factory complex in Bangladesh passed 500 after dozens more bodies were pulled out from the wreckage overnight, the army said.
"The death toll now stands at 501," Lieutenant Mir Rabbi of the army control room, which was set up to coordinate the recovery operation, told AFP.
It's the deadliest disaster to Bangladesh's $US20 billion ($A19.60 billion)-a-year garment industry that supplies global retailers
