Federal safety investigators are looking at structural problems and a dust explosion as possible causes of an industrial building collapse in Omaha that killed two workers and injured 17 others.

Federal Occupational Safety and Health Administration spokesman Scott Allen says investigators are working with structural engineers and combustible dust experts as part of their investigation into Monday's collapse of the International Nutrition building in southwest Omaha. The plant makes nutritional products that are added to livestock and poultry feed.

Allen said Wednesday that it likely will be weeks before investigators identify a cause of the collapse.

He says OSHA investigators were able to enter the heavily-damage building Tuesday and gather some evidence and photos but declined to say what that evidence included.