U.S. health officials Wednesday said four more people have died from rare fungal meningitis, bringing the number of deaths in the outbreak to 19.

There are at least 245 confirmed cases in 15 states, and thousands of others may also be infected.

Nearly all the victims were injected for back pain with a contaminated steroid made by the now-closed New England Compounding Center — a specialty pharmacy in Massachusetts.

Agents raided the pharmacy's offices on Tuesday. The raid was part of a federal investigation that the center may have broken the law by making mass doses of a medicine instead of made-to-order prescriptions.

Officials said last week that more than 50 vials of the steroid tested positive for the fungus. Health experts say thousands of patients in 23 states may have gotten the contaminated medicine. They say it could take several months for symptoms of meningitis to appear.

Meningitis is a disease infecting membranes protecting the brain and spinal cord. There are five different types. Fungal meningitis is the rarest form. Other types are cased by bacteria, a virus or a parasite.