An investigator probing the Bangladesh garment factory disaster in which more than 500 people died says the building could not withstand vibrations from large generators on the upper floors.
The government is investigating the catastrophic structural failure of the eight-storey building in Savar, about 30 kilometres to the north-west of the capital, Dhaka, on the morning of 24 April.
Senior home ministry official and lead investigator Main Uddin Khandaker said four large generators were set up on each of the top floors where garment factories were located, violating rules.
He said when they were started after a power cut, they created vibrations and, together with the vibrations of thousands of sewing machines, triggered the collapse.
Mr Khandaker told AFP the building, Rana Plaza, was built for commercial use not factory use, and could not withstand the vibrations because the owner used substandard rods, bricks and other materials in its construction.
It also emerged on Friday that an engineer who had warned before the collapse that the building might be unsafe was being questioned by police after becoming the latest person to be arrested over the disaster.
With bulldozers clawing away at the mountain of rubble at the site, the number of bodies being recovered from the country's deadliest industrial disaster has been increasing sharply, AFP reports.
Captain Shakiur Rahman, an officer in a special army control room set up to co-ordinate the rescue operation, said the death toll stood at 525.
Dozens more people are thought to have been buried alive. About 3000 garment workers sewing clothes for Western brands were on shift at the time of the disaster in the Rana Plaza compound, which housed five different textile factories.
Spain's Mango, Britain's low-cost Primark chain and the Italian label Benetton were among the retailers who have confirmed having products made at the site, where the typical worker took home less than $US40 a month.
The collapse - the latest in a series of disasters to befall the $US20 billion industry, which accounts for 80% of the country's exports - has focussed attention on the clothing industry's global supply chain.
