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Two members of Congress have asked the U.S. Department of Justice to investigate whether a specialty pharmacy linked to a nationwide meningitis outbreak violated any federal laws or regulations.

The number of illnesses associated with contaminated steroid shots distributed by New England Compounding Center climbed to 233 in 15 states, the Centers for Disease Control reported Tuesday. Fifteen people have died.

Criminal investigators from the Food and Drug Administration were at the Framingham company Tuesday, company spokesman Andrew Paven said. He had no further comment.

FDA spokesman Steven Immergut said the investigators were there as part of the broad investigation by several state and federal agencies into the outbreak.

Boston U.S. Attorney Carmen Ortiz confirmed that her office is part of the investigation. "I think that it is entirely premature to suggest what the results of the investigation will be," she said.

Rep. Edward Markey, D-Massachusetts, wrote in a letter to the Justice Department that the list of products recalled by the company appears to include controlled substances that fall under the jurisdiction of the Drug Enforcement Agency.

The DEA requires pharmacies that sell or compound controlled substances to be registered with the agency, which NECC was not, Markey wrote. He added that the rules only allow pharmacies to sell controlled substances directly to patients with specific prescriptions unless the pharmacy registers with the DEA as a manufacturer or supplier.

"This is a matter that I believe requires further investigation by the DEA to ensure that this facility, already believed to have broken Massachusetts state law, has not also skirted federal law related to controlled substances," said Markey, a member of the Energy and Commerce Committee in whose district the Framingham, Mass., company is located.

Gov. Deval Patrick said last week that NECC might have misled regulators and done work beyond the scope of its state license. Federal and state investigators have said they have found fungus in more than 50 vials from the company, but they have not said whether they have pinpointed the source of the contamination.

In a recent letter to U.S. Attorney General Eric Holder, Sen. Richard Blumenthal, a Connecticut Democrat, also called for a criminal investigation of the company, its officers and employees, pointing to reports that NECC "may have flagrantly and blatantly violated both state and federal law."

The Justice Department in Washington had no immediate comment on the letters.

NECC, in a statement, did not directly respond to the legislators but said it was cooperating with ongoing probes by other agencies.

"We continue to cooperate with the FDA, as we are with the CDC and the Board of Registration in Pharmacy of the Massachusetts Department of Public Health. As we have said, we will respect those public agencies' processes for investigations and will not comment while they are underway," the company said.

The CDC said Tuesday that 231 of the reported illnesses were cases of fungal meningitis linked to shots for back pain and two others were nonfatal joint infections.

Markey also planned to file legislation that he said would strengthen the FDA's oversight of compounding agencies and tighten gaps in federal regulations.