(CNN) -- A Massachusetts pharmacy linked to a meningitis outbreak says its cleaning contractor should share blame for the apparent mishap that left dozens dead nationwide.
The New England Compounding Center sent a letter to UniFirst Corp. demanding it share responsibility for a tainted steroid used to treat pain and inflammation, according to a filing this week with the Securities and Exchange Commission.
UniFirst Corp. acknowledged that it provided "once-a-month cleaning services," but added that the pharmacy's claims are "without merit," the filing says.
Last week, the compounding center announced that it had filed for bankruptcy protection under Chapter 11.
The company said that it "seeks to establish a fund to compensate individuals and families affected" by the outbreak, which has been linked to 39 fatalities among the 656 cases tallied in 19 states.
Patients contracted fungal meningitis -- which results in inflammation of the membranes covering the brain and spinal cord -- after their spines were injected with a contaminated, preservative-free steroid called methylprednisolone acetate, health officials have said.
According to health agencies, the compounding center did not follow proper sterilization procedures and distributed its products without knowing whether they had passed sterility tests.
In addition, it distributed vials containing a steroid that was contaminated with "visible black particulate matter" later identified as fungus, according to a report from the Massachusetts Board of Registration in Pharmacy.
The contamination problem came to light in the fall, after the first fungal meningitis cases were reported. The New England Compounding Center voluntarily recalled three lots of the steroid in September.
In October, the pharmacy board, which is part of the state's Department of Public Health, said it had "identified serious deficiencies and significant violations of pharmacy law and regulations that clearly placed the public's health at risk."
The Food and Drug Administration and the Centers for Disease Control and Prevention have said they have identified bacterial and/or fungal contamination in unopened vials of some of the compounding center's products.
The U.S. House Energy and Commerce Committee's Subcommittee on Oversight and Investigations is looking into what went wrong at the company and why it was allowed to continue to function despite a history of problems.
Federal authorities have launched a criminal investigation into the practices at the Framingham-based company, and the state pharmacy board has voted to permanently revoke the company's license to operate as well as the licenses of the company's three principal pharmacists.
Symptoms of fungal meningitis can include headache, fever, nausea, stiff neck, weakness or numbness anywhere in the body, slurred speech, pain or swelling at the injection site and sensitivity to light, according to the CDC.
Treatment, which can have toxic side effects, is expected to continue for infected patients for "many months," Dr. John Jernigan told reporters last month. He leads the CDC's meningitis outbreak clinical team.