U.S. health authorities say a contaminated steroid suspected of causing five fatal cases of rare fungal meningitis may have been given to thousands of patients.

The company that manufactured the suspect medicine, the New England Compounding Center in Massachusetts, has been shut down. It has recalled the steroid. The U.S. Centers for Disease Control and Prevention found a sealed vial at the company that was contaminated with a fungus. They are investigating if it is the same fungus that caused the meningitis outbreak.

Thirty-five people in six eastern states injected with the steroid for back pain have been infected. Five of them have died. The CDC believes thousands of people in 23 states may have received contaminated injections. It could take up to one month for the symptoms to appear.

Meningitis is a disease that infects membranes protecting the brain and spinal cord. There are five different types of meningitis. The current outbreak is caused by a fungus and doctors say it is a very rare form of the disease.

Others types are caused by bacteria, a virus, or a parasite.