NEW YORK — The fungus found in tainted steroid shots matches the one behind the national meningitis outbreak that has killed 20 people, federal health officials said Thursday.

The match confirms the link between the outbreak and the maker of the steroids, New England Compounding Center of Framingham, Mass. Officials previously said they found fungus in more than 50 unopened vials from the company, but needed more tests to determine the kind of fungus.

The specialty pharmacy has been at the center of a federal and state investigation into more than 250 fungal meningitis cases. The death toll rose Thursday to 20.

The victims in the outbreak had all received steroid shots made by the pharmacy, mostly to treat back pain. The company last month recalled three lots of the steroid made since May. It later shut down operations and recalled all the medicines it makes.

The fungus was confirmed in one steroid batch made in August, according to the Food and Drug Administration and the Centers for Disease Control and Prevention. The CDC has linked outbreak illnesses to all three lots; tests are continuing on the other two lots.