The U.S. Food and Drug Administration has sent a warning letter to St. Jude Medical regarding manufacturing processes at a facility in Southern California, St. Jude and the FDA have confirmed.

Until St. Jude corrects the issues that prompted the letter, the FDA will not approve certain types of cardiac rhythm management products from the Little Canada-based medical technology company, the company confirmed Monday. The plant in Sylmar, Calif., is where St. Jude manufactures the Durata defibrillator lead, a wire that connects the defibrillator to the heart.

FDA inspectors visited the facility from Sept. 25 to Oct. 17, 2012. The inspection raised several concerns with regulators, prompting them to file what is called a Form 483 detailing alleged violations at the facility. For example, the Form 483 cited concerns over such things as the number of tests performed on Durata leads and the facility's record-keeping.

According to St. Jude, the warning letter will not affect sales of existing St. Jude products. It also will not delay approval requests for other new, non-cardiac rhythm products from St. Jude, the company said.

The letter, dated Jan. 10 and received by St. Jude the next day, is not yet public, according to an FDA spokeswoman. It will be made public when the agency posts the document on its website, said spokeswoman Sarah Clark-Lynn. St. Jude also would not release a copy of the warning letter before it is posted by the FDA, said a company spokeswoman.

The letter does not raise any safety concerns about the Durata lead, other St. Jude leads or any other St. Jude products, St. Jude said.

"Accordingly, the company will continue manufacturing and shipping product from the Sylmar facility and customer orders are not expected to be impacted while we work to resolve the FDA's concerns," St. Jude said in a document posted Monday with the Securities and Exchange Commission.

St. Jude officials have been expecting this for months.

In an effort to calm the FDA's concerns, St. Jude on Nov. 7 sent a 34-page letter to the FDA, acknowledging mistakes and promising to make improvements and bolster training.

In a statement issued last week, St. Jude said it "takes quality and product safety very seriously." St. Jude stressed that the FDA's concerns "centered on the company's internal quality system processes. It is important to note that none of the observations identified any specific issues with the clinical or field performance of any St. Jude Medical products."

On Monday, St. Jude said in its SEC filing that it "takes this matter seriously and has already begun to respond to the FDA's requests. The company is giving the highest priority to fully remediating these concerns."

Some analysts and physicians have said they are taking a wait-and-see approach to St. Jude's assertions as the market has proven skittish over any possibility of trouble with the company's pacemaker and defibrillator leads.

In November, after it was discovered that the FDA had raised concerns over processes concerning Durata, St. Jude's share price fell nearly 13 percent. Company officials had earlier disclosed that they could receive a warning letter from the FDA over the Sylmar facility -- but did not say those concerns concerned Durata.

Durata has been the company's primary defibrillator lead since St. Jude pulled its Riata leads off the market in late 2010, following safety concerns arising when inner wires were found to have worked their way through the lead's insulation. Nothing has indicated that Durata has had similar problems to the Riata lead.

St. Jude shares rose 56 cents Monday to close at $38.85.

In the posting with the SEC, St. Jude officials said the company has taken the circumstances surrounding the warning letter "into account in managing its business and setting investor expectations, and believes the FDA's concerns can be resolved without a material impact on the company's financial results."

St. Jude officials are scheduled to give their financial guidance for 2013 during the company's fourth quarter earnings conference call, set for Jan. 23.

James Walsh • 612-673-7428