NASHVILLE, Tenn. (AP) -- Tennessee and federal health experts are investigating an outbreak of meningitis that infected 14 people who received steroid injections, killing two of them, the state's chief medical officer said Tuesday.

Dr. David Reagan, chief medical officer for the Tennessee Department of Health, said the latest two cases were confirmed in the past 24 hours. All but one of those who contracted the infection had received steroid injections for back pain at a Nashville clinic, authorities said.

The other case was reported in North Carolina in a patient who had received the same type of injection, authorities said.

Marion Kainer, an infectious diseases physician and epidemiologist with the Tennessee Health Department, said it's still too early to pinpoint the source. But Kainer said three lots of injectable steroid used at a Nashville clinic between July 30 and Sept. 20 have been recalled by the manufacturer. The clinic, the Saint Thomas Outpatient Neurosurgery Center, voluntarily shut its doors Sept. 20.

"This is a serious illness, a serious disease," Kainer said. "There is not a lot of experience treating it, but we're getting the best advice possible."

Officials haven't identified the drug manufacturer or the city in North Carolina where one of the cases was reported. Reagan said that publicizing too much information at this time could negatively affect the investigation.

Centers for Disease Control and Prevention spokesman Curtis Allen said the agency is working with health departments in other states to determine whether other patients might be affected. He could not say how many people or clinics could potentially be affected nationally. In Tennessee there are about 900 people who received the injections at two clinics during the timeframe under investigation. No one from the second clinic has at this time been found to have contracted the disease, officials said.

Allen cautioned that while the injectable steroids were one thing the sickened patients had in common, there could also be other things in common, such as the anesthetic or the antiseptic, and the search for a cause is ongoing.

Of the 11 surviving patients in Tennessee, some are in critical condition while others are improving, Reagan said.

Thus far, it has taken patients between seven days and 28 days to develop symptoms, said Health Department spokesman Woody McMillin. Officials say new cases could be identified in coming days.

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