The death toll from the meningitis outbreak linked to a contaminated steroid drug rose to 16 on Tuesday night as a leading medical expert said the infections were "nowhere near the end".

William Schaffner, an infectious diseases expert at the Vanderbilt University Medical Center in Nashville, said he expects a "steady increase" in the number of fungal meningitis infections over the coming weeks.

His warning came as the Virginia health department confirmed that a second person had died in the state, just hours after the Centers for Disease Control said the number of cases had increased by 19 to 231. It also reported two cases of peripheral joint infections.

Earlier on Tuesday federal agents raided the New England Compounding Center, the pharmacy linked to the outbreak. US Attorney Carmen Ortiz, the top federal prosecutor in Massachusetts said agents from the Food and Drug Administration searched the NECC facility in Framingham.

Schaffner described the escalating FDA investigation into further NECC products as "ominous" and said they would have to warn more patients.

"We were concerned that there might be other medications that might be contaminated coming from that pharmacy," said Schaffner, a past president of the National Foundation for Infectious Disease. "The FDA has given us a heads up that that looks to be the case. We'll have to notify many more patients across the country that they may have been exposed to a fungal infection."

On Monday, after reporting unconfirmed infections from two more drugs made by the NECC, the FDA told medical personnel to contact all patients injected with any drug from the pharmacy, in particular heart transplant and opthalmic patients, as a precautionary measure, to alert them of the risk of infection.

The advice has confused some clinicians who accused the FDA of sending mixed messages which may panic patients.

During a conference call with clinicians and journalists on Tuesday, Dr Janet Woodcock of the FDA stressed that no other NECC products have been confirmed as being linked to the outbreak, but they were investigating such products following at least one infection in a heart transplant patient.

"None of the infections have been confirmed" said Woodcock. "No other products have been linked to documented infections."

Asked if they were in danger of issuing mixed messages in danger of scaring patients, Woodcock said: "I don't think we are asking you to tell them they should be concerned, we are asking you to reach out to them make sure they are healthy and they are no signs of infections."

The infections in patients that have been linked to two new drugs made by NECC, particularly that of a heart transplant patent, who are susceptible to infections, could have arisen from another source, officials said.

Already, 14,000 patients at risk from contracting the disease after having been injected with a potentially contaminated steroid, methylprednisolone, are on the lookout for symptoms of meningitis.

Asked about the spread of the outbreak, Schaffner said: "I think we're still in the middle. We're nowhere near the end of this problem. And we will see more patients reporting in ill and we'll have to treat many more going forward."

Hospitals, clinics and physicians have already been warned not to use any product made by NECC, as well as to contact patients who may have had an injection of the steroid associated with the 15 deaths.

So far, those infected with meningitis have received a spinal injection of the steroid as a treatment for back pain.

On Monday, the agency said it had reports of three patients, including two transplant patients, with possible meningitis who received an injection of another steroid made by NECC.

On Tuesday, the FDA issued a revised statement on its website saying that it was one transplant patient. The patient, who had received a heart drug known as cardioplegia solution made by NECC, had Aspergillus infection but the FDA said there may be another explanation for the infection.The investigation was ongoing, it said.

The second patient identified by the FDA as potentially having meningitis received an injection of the steroid triamcinolone, also supplied by NECC.

It cautioned that any injectable drugs made by NECC, including those intended for use in eyes, are of "significant concern".

The statement on the FDA website said:

At this point in FDA's investigation, the sterility of any injectable drugs, including ophthalmic drugs that are injectable or used in conjunction with eye surgery, and cardioplegic solutions produced by NECC are of significant concern, and out of an abundance of caution, patients who received these products should be alerted to the potential risk of infection.



It also advised physicians and medical personnel to "follow-up with patients for whom you administered an injectable product, including an ophthalmic drug that is injectable or used in conjunction with eye surgery, or a cardioplegic solution purchased from or produced by NECC after May 21, 2012."

The FDA said they were still investigating the two infections found in patients who had received cardioplegia and triamcinolone made by NECC to see if they were linked.

The NECC said in a statement that it was reviewing the new information from the FDA.

On Monday a Tennessee woman who contracted fungal meningitis after receiving an epidural injection with the NECC-prepared steroid filed a lawsuit against the company seeking $15m in damages. Tennessee has been the hardest-hit state, with 53 cases and six deaths.

Meningitis is an infection of the membranes covering the brain and spinal cord. Symptoms include headache, fever and nausea. Fungal meningitis, which also causes strokes, is not contagious.

All but eight of the 23 states that received suspect medications from the Massachusetts specialist pharmacy have reported at least one case of fungal meningitis, a rare and deadly disease that has proven difficult to treat.

The suspect lots of steroid were shipped to 76 facilities.

A list of recalled NECC products on the FDA website ran 70 pages.

The outbreak has raised questions over the oversight of pharmacies known as compounding centers, which are not directly regulated by the FDA.

In compounding, pharmacies prepare specific doses of approved medications, based on guidance from a doctor, to meet an individual patient's need.

However, state pharmacy regulators have said that NECC violated its license in Massachusetts by not requiring patient prescriptions before shipping products.

The 15 states reporting cases of meningitis are Tennessee, Michigan, Pennsylvania, New Hampshire, Illinois, Indiana, Minnesota, New Jersey, Texas, Idaho, Maryland, North Carolina, Virginia, Ohio and Florida.