(CNN) -- The company at the center of a deadly meningitis outbreak was warned by its own environmental monitors of bacterial contamination of its facility months before the first cases were reported, a government report said Friday.

Mold, and in some cases, an overgrowth of bacteria was detected in different areas of the New England Compounding Center's two "clean rooms" nearly 90 times since January, the Food and Drug Administration report said.

Clean rooms are intended to be sterile environments in which drugs are produced.

Despite the warnings from its own monitors, the FDA report says the compounding center did not investigate the reports of the contamination nor is there documented evidence it worked to decontaminate the affected areas.

Tainted medications from the compounding center have been blamed for the outbreak of fungal meningitis that has caused 25 deaths and 338 illnesses.

The FDA's preliminary findings were released following an inspection of the compounding center this month. In addition to documented reports of bacterial contamination, FDA investigators observed "greenish black foreign matter" and "white filamentous material" in vials of methylprednisolone acetate -- the steroid linked to the meningitis outbreak.

The Framingham, Massachusetts-based compounding center acknowledged receiving the report Friday, but declined to comment beyond saying it will review the findings.

"We will follow the existing regulatory process and provide our comments to the FDA after we have had adequate time for a complete review of the report," the company statement said.

The FDA report comes the same week that the Massachusetts Board of Registration in Pharmacy voted to revoke permanently the compounding center's license to operate in the state as well as the licenses of the company's three principal pharmacists.

A damning nine-page report released Tuesday by the same state board "identified serious deficiencies and significant violations of pharmacy law and regulations that clearly placed the public's health at risk."

Federal authorities have launched a criminal investigation into the center's safety practices.

Authorities were first alerted to the outbreak when a cluster of six rare fungal meningitis cases were reported in Tennessee on September 24. The patients shared several risk factors, including an epidural injection of a steroid -- methylprednisolone acetate 80 mg/ml preservative free -- that had been compounded at the center.

Since then, the outbreak has grown to 18 states.
FDA: Drug company's own monitors warned of contamination months before outbreak