The death toll from a widening outbreak of fungal meningitis linked to steroid injections has risen to seven, with 65 cases now reported in nine states, officials said on Saturday.

The latest two deaths were reported on Saturday in Michigan, according to the US Centers for Disease Control and Prevention.

Those affected fell ill after receiving steroid injections linked to a pharmaceutical compounding plant in Massachusetts.

New cases in Ohio and Minnesota on Saturday brought to nine the number of states affected, officials said.

Other states with reported cases of people who fell ill after receiving the injections - primarily for back pain - are Michigan, Tennessee, Virginia, Florida, Maryland, North Carolina and Indiana.

Meningitis is an infection of the membranes covering the brain and spinal cord.

Vials of steroids linked to the outbreak were shipped to 76 facilities in 23 states and could have been used to inject thousands of patients, authorities have said.

As in other states where the outbreak has been detected, Minnesota authorities are trying to determine who else may have been infected at six locations known to have used the drugs in question, said Buddy Ferguson, public information officer for the state's Department of Health.

"We have identified a list of approximately 950 people who did receive injectable steroids from the implicated lots," he said, adding authorities were in the process of contacting each patient.

Tennessee, where the outbreak was first detected, accounts for most of the cases, with 29, state officials said on Friday.

Three of the deaths have been in Tennessee, and one each in Virginia and Maryland.

In Tennessee, many patients remain hospitalised, some listed in critical condition.

The infected patients have shown a variety of symptoms from one to four weeks after their injections, including fever, a new or worsening headache, nausea and neurological problems that would be consistent with deep brain stroke, the CDC said.

All the cases have been traced to three lots of the steroid prepared at New England Compounding Center in Framingham, Massachusetts. The company said it had suspended its operations while the investigation proceeds.

The Massachusetts Health Department said there were 17,676 vials of medication in each of three lots of methylprednisolone acetate sent out from July through September and have a shelf life of 180 days.

So far, the tally of cases includes 29 in Tennessee, 11 in Virginia, eight in Michigan, five in Indiana, four in Florida, three in Maryland, two in North Carolina, two in Minnesota and one in Ohio.

The steroid was sent to California, Connecticut, Florida, Georgia, Idaho, Illinois, Indiana, Maryland, Michigan, Minnesota, North Carolina, New Hampshire, New Jersey, Nevada, New York, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Texas and West Virginia, the CDC said. – Reuters