Story highlights At least 14 people have died from the outbreak, official says

Some 51 people have died nationwide, the CDC says

"This investigation is necessary to uncover the truth," attorney says

Michigan's attorney general has requested a criminal investigation into the conduct of an embattled Massachusetts company linked to a recent deadly fungal meningitis outbreak.

Michigan had at least 259 infections and 14 deaths, leading the nation in people affected by the outbreak last year, said Bill Schuette, the state's attorney general.

The outbreak, linked to tainted steroid injections from New England Compounding Center, killed 51 people and infected 730 people in 20 states, the Centers for Disease Control and Prevention said.

"Hundreds of Michigan citizens and their families have endured terrible pain and deaths of loved ones suffering from illnesses caused by these tainted steroid injections," said Schuette. "This investigation is necessary to uncover the truth as to how this unspeakable tragedy happened and to restore public faith in our healthcare system."

Schuette said he filed a petition to the Michigan Court of Appeals to have a grand jury determine if the company broke any state laws "when it distributed tainted steroid injections to patients at clinics in four Michigan counties."

JUST WATCHED 2012: Meningitis victim mourned Replay More Videos ... MUST WATCH 2012: Meningitis victim mourned 03:29

A representative of the New England Compounding Center could not immediately be reached for comment.

Barry Cadden, owner and director of the company, was summoned to a congressional subcommittee in November but refused to answer questions, citing his constitutional right to remain silent.

The company filed for bankruptcy in December . Also last year federal authorities launched a criminal investigation into the practices at New England Compounding Center.

A state pharmacy board also 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, new weakness or numbness anywhere in the body, slurred speech, pain or swelling at the injection site and sensitivity to light, according to the CDC.