A government probe into the tragic collapse of a multi-storey factory building in Bangladesh has uncovered a series of violations that ultimately led to the death of more than 1,100 garment workers.

The investigation revealed poor construction materials and building code violations were among the irregularities that caused the disaster.

“The owner used extremely poor quality iron rods and cement,” committee head Khandker Mainuddin Ahmed told The Associated Press. “There were a series of irregularities”.

The building was not built for industrial use and the weight of the heavy garment factory machinery and the vibration it caused contributed to the building collapse, according to the report.

The report found Sohel Rana, the owner of the building, had permission to built a six-storey structure but added two floors illegally to rent them out to garment factories. A portion of the building was also constructed on unsuitable land.

It also recommended life sentences for Rana and the owners of five garment factories operating there.

The collapse, one of the world’s worst industrial disasters, highlighted working conditions, low wages and a lack of safety standards in Bangladesh’s large garment sector.