Updated

A government investigation says poor quality construction materials and building code violations contributed to the collapse of building housing garment factories last month in Bangladesh.

Committee head Khandker Mainuddin Ahmed told The Associated Press on Thursday a series of irregularities occurred in the construction of Rana Plaza. Its collapse killed more than 1,100 workers and was one of the world's deadliest industrial disasters.

Ahmed says the building owner used "extremely poor quality of iron rods and cement." The report says the owner had permission for a six-story structure and added two floors illegally. Past information said the owner had permission for a five-story structure and added three.

The report sent to the government Wednesday also recommends life prison terms for those found guilty of violating building codes in the case.