The death toll from fungal meningitis rose to 23 today as the outbreak claimed a life in North Carolina.
The Guardian reported 16 US states have now been affected, with the number of reported cases continuing to climb. As of yesterday, it stood at 284, the Centers for Disease Control and Prevention (CDC) said.
It said the victims had all received steroid shots made by the New England Compounding Center (NECC) in Massachusetts, mainly to treat back pain.
Reuters reported on Thursday it was confirmed the presence of a deadly fungus in one of three lots of steroids used.
"The laboratory confirmation further links steroid injections from these lots from NECC to the multi-state outbreak of fungal meningitis and joint infections," the FDA announced in a news release, the Los Angeles Times reported.
Authorities, who are continuing tests of the other two lots of drugs, estimate that about 14,000 patients were exposed to the contaminated medication, which was mainly given to older patients.
So far 254 cases have been reported, including the first yesterday in New York - the 16th state to be affected.
Dr Tom Chiller, an epidemiologist with the Centers for Disease Control and Prevention, told Reuters: "Now we can definitively say that the injections are linked to the infection."
"To date, CDC has no firm evidence of infection in any patients beyond those exposed to the contaminated lots."
BBC News reported the New England Compounding Center faces federal and state investigations, as well as civil lawsuits.
The company recalled last week 17,000 vials of steroid that had been sent to more than 70 clinics in America.