The Food and Drug Administration announced Friday it had issued a warning to a California company for making and selling unapproved umbilical cord blood products, and for “significant deviations” from safety practices that create serious risks for patients injected with the stem cell therapy.

A year ago, the company, Liveyon, based in Yorba Linda, was tied to the distribution of another manufacturer’s contaminated umbilical cord blood products that sickened 12 people in three states. The Washington Post reported in February that at least 17 people had been hospitalized after being injected with umbilical cord blood products, most of which were sold by Liveyon. Some of the patients were in the hospital for weeks.

The FDA action is part of an effort to clamp down on stem-cell products that are not approved by federal regulators or supported by clinical research, and may endanger consumers. Businesses selling the products say they provide relief to many patients, but many scientists are skeptical and liken the treatments to snake oil. It requested a response from the companies in 15 days on how the issues will be corrected. Failure to correct the problems could lead to seizure, injunction or prosecution, the agency said.

The FDA’s warning letter, dated Dec. 5, went to Liveyon Labs, which processes umbilical cord blood to make products called Pure and Pure Pro, and its distributor, Liveyon LLC. The products are marketed mainly as a treatment for patients with back, knee and other joint problems.

The FDA said a May inspection showed the companies were making and selling products that are considered drugs although they did not have the approval to do so. It also said the companies failed to screen donors adequately for communicable diseases; and didn’t follow procedures to prevent microbiological contamination or establish a system for cleaning and disinfecting the processing room and equipment.

The FDA said that Liveyon took some “corrective actions” after the May inspection, but that the response did not provide enough detail “to fully assess the adequacy” of the changes or address its failures to not have required approvals.

“The agency is aware that there are establishments who prey upon vulnerable populations by commercially marketing stem cell products with false and misleading claims about their effectiveness for treating serious diseases,” said Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research. “The FDA is taking this action today because Liveyon Labs and Liveyon LLC failed to take appropriate measures to protect patient safety.”

In a statement, the company said the FDA “has acknowledged Liveyon’s subsequent improvements” but was requesting “additional corrective action, including proof of updated policies and procedures.” It said it would cooperate with the FDA.

Last November, the FDA issued a issued a similar warning to San Diego-based Genetech for manufacturing an umbilical cord product that Liveyon sold. Liveyon conducted a voluntary recall and began making its own products, Pure and Pure Pro, earlier this year.

The agency on Friday also sent “untitled letters” — which are less serious than warning letters — to two other companies for selling unapproved therapies.

William Wan contributed to this report.

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