The U.S. Food and Drug Administration said on Friday it found "greenish black foreign matter" and other contaminants in an injectable steroid produced by the New England Compounding Center, the pharmacy at the heart of a deadly U.S. meningitis outbreak.

It also found that vials from the same bin of the steroid contained what appeared to be a "white filamentous material," according to the report released by the FDA following inspections of the facility in October.

Massachusetts health regulators said earlier this week that they had turned up evidence of problematic procedures, record-keeping and work conditions inside the pharmacy facility.

The pharmacy is being investigated for its role in the meningitis outbreak, which has killed 25 people and infected hundreds who received injections of its preservative-free methylprednisolone acetate, a steroid used for back pain and other conditions.

The FDA report also said that NECC's environmental monitoring program found bacteria and mold in two "clean rooms" between January 2012 and September 2012. The rooms are used in the production of sterile drug products.