Dirty shoes? How did steroids get contaminated?

A Food and Drug Administration Agent stands at the doorway of New England Compounding Center in Framingham, Mass., Tuesday, Oct. 16, 2012, as investigators work inside. The company's steroid medication has been linked to a deadly meningitis outbreak. FDA spokesman Steven Immergut says the visit is part of the investigation into the outbreak, which has killed at least 15 people and sickened more than 200 others in 15 states. (AP Photo/Bill Sikes)Was it some moldy ceiling tiles? The dusty shoes of a careless employee? Or did the contamination ride in on one of the ingredients?