Home minister Asaduzzaman Khan rejects the allegations, says the detentions were lawful and accuses New York-based Human Rights Watch of spreading "propaganda".
Dozens of labourers were on site at the factory when a boiler exploded at the six-storey building, causing its walls and a roof to collapse.
The fire was caused by an explosion in the boiler room of the factory in Tongi, just north of the capital Dhaka.
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