OMAHA, Neb. -- The cause of an explosion at a plant in Omaha that killed two people is under investigation.

That blast rocked the International Nutrition Plant killing two and injuring 10 others.

Investigators say they are unsure what set off the explosion but they do know the building's support beams failed, sending the second and third floors crashing onto the first floor.

The Omaha Interim Fire Chief says the investigation could take weeks.