Bangladeshi garment factories are routinely built without consulting engineers.
Many are located in commercial or residential buildings not designed to withstand the stress of heavy manufacturing.
Some add illegal extra floors atop support columns too weak to hold them, according to a survey of scores of factories by an engineering university that was shown to The Associated Press.
A separate inspection, by the garment industry, of 200 risky factories found that 10 per cent of them were so dangerous that they were ordered to shut.
The textiles minister said a third inspection, conducted by the government, could show that as many as 300 factories were unsafe.
Taken together, the findings offer the first broad look at just how unsafe the working conditions are for the garment workers who produce clothing for major western brands.
And it's more bad news for the USD 20 billion industry that has been struggling to regain the confidence of Western retailers and consumers following a November fire at the Tazreen Fashions Ltd factory that killed 112 people and the April collapse of the Rana Plaza building that killed 1,129 people in the worst garment industry tragedy.
But the proliferation of inspections could signal the industry is finally taking its workers' safety seriously.
Rana Plaza was "a wakeup call for everybody" to ensure their buildings were structurally sound, said Shahidullah Azim, vice president of the Bangladesh Garment Manufacturers and Exporters Association.
"Earlier it was not in our minds. We never, ever thought of this," he said.
But Rana Plaza wasn't the first factory building to collapse in Bangladesh. In 2005, the Spectrum sweater factory crumbled on top of workers, killing 64. That building was also found to have illegal additions.
After the Rana collapse, the government and the garment manufacturers asked the Bangladesh University of Engineering and Technology to begin evaluating the buildings.
