Health officials on Thursday reported an outbreak of bacterial infections in people who got injections of stems cells derived from umbilical cord blood.

Axar.az reports that at least 12 patients in three states — Florida, Texas and Arizona — became infected after getting injections for problems like joint and back pain, the Centers for Disease Control and Prevention said. All 12 were hospitalized, three of them for a month or longer. None died.

Investigators don't think the contamination occurred at the clinics where the shots were given, because they found bacteria in unopened vials provided by the distributor, Yorba Linda, California-based Liveyon. Liveyon voluntarily recalled the stem cells in October.

Last month, the Food and Drug Administration sent a warning to Genetech Inc., the small San Diego company that processed the stem cells. The FDA said the company should not be marketing the stem cells without regulators' approval and has deviated from manufacturing requirements in ways that could have led to bacterial contamination.

Last year, the FDA announced plans to crack down in doctors and businesses promoting stem cell injections for diseases ranging from arthritis to Alzheimer's disease.

The CDC reported that stem cells from cord blood were the source of bacterial infections in seven in Texas, four in Florida and one in Arizona. The average age of the patients was 74.