NASHVILLE, Tennessee (Reuters) - More cases of fungal meningitis tied to contaminated steroid shots are expected to be confirmed on Tuesday, U.S. health officials said, and some patients who received the injections may have to wait weeks to know if they are infected.

Since the September 25 recall of three lots of a steroid produced by a Massachusetts company, the outbreak has spread to nine states and 105 patients, with eight people killed, the Centers for Disease Control said.

As many as 13,000 people received the injections and are at risk of infection, the CDC said, although the number ultimately stricken is likely to be far fewer.

The outbreak has alarmed health officials and highlighted a gap in regulation of so-called pharmacy compounders, which are facilities that take drug ingredients and package them into medications and dosages for specific clients.

The federal Food and Drug Administration regulates only the ingredients and not the compounders, which are subject to a patchwork of state oversight.

Some of the thousands of people exposed may have to wait anxiously for weeks because the incubation period of the disease is up to a month, health experts said.

"Infected patients have (come forward) approximately one to four weeks following their injection with a variety of symptoms including fever, new or worsening headache, nausea and other new symptoms consistent with a stroke," the CDC's Dr Benjamin Park has said.

The number of cases rapidly increased as health practitioners at 76 facilities in 23 states notified those who received the shots and patients were examined.

Tennessee is the hardest hit state with 35 cases confirmed so far, and one hospital, Saint Thomas in Nashville, received about 2,000 vials from the steroid supplies recalled by the company.

"The response from Saint Thomas Hospital has been dramatic," said Dr Robert Latham, the hospital's chief of medicine. "We've seen upwards of 40 to 50 patients a day since last Monday through the emergency room that have had to be extensively evaluated."

The nine states with cases are Tennessee, Indiana, Ohio, Minnesota, Michigan, North Carolina, Virginia, Maryland and Florida.

Four people have died in Tennessee, two in Michigan and one each in Maryland and Virginia.

Meningitis is an infection of the membranes covering the brain and spinal cord. It is not contagious.