DHAKA: Bangladesh police have arrested three managers of a factory where a blaze killed 110 people, following claims they stopped workers from leaving the plant saying an alarm was just a routine fire drill.

Dhaka police chief Habibur Rahman told AFP Wednesday the managers were arrested overnight after charges that they told panicked workers of Tazreen Fashion they had nothing to worry about when the fire started on Saturday night.

“All three are mid-level managers of Tazreen. Survivors told us that they did not allow the workers to escape the fire, saying that it was a routine fire drill. There are also allegations that they even padlocked doors,” he said.

Survivors and witnesses told AFP how workers, most of them women, tried to escape the burning factory, which supplied clothes to international brands including Walmart, European chain C&A and the Hong Kong-based Li & Fung company.

Two government inquiries have already been set up to try to establish the cause of the fire, the worst factory blaze to hit Bangladesh's garment industry, which employs three million and is the mainstay of the economy.

The shell-shocked nation observed a day of national mourning Tuesday. Green and red Bangladeshi flags flew at half mast alongside black flags on top of government offices and the nation's 4,500 garment factories.

Rahman said police also quizzed Tazreen's owner, Delwar Hossain, about alleged violations of building rules after inspectors found the nine-storey factory only had permission for three floors.

Around 700 garment workers have been killed in dozens of fires since 2006, according to the Clean Clothes Campaign, an Amsterdam-based textile rights group. But none of the owners have been prosecuted over previous blazes.

Campaigners say Western firms whose clothes are made in Bangladesh hide behind flimsy safety audits to help drive down costs.

After European chain C&A and Hong Kong-based Li & Fung confirmed they had orders at Tazreen, the US retail giant Walmart also acknowledged some of its products were made there and said it had terminated ties with the supplier.