The Food and Drug Administration (FDA) announced last week the latest in an already widespread recall of common blood pressure and heart failure medications.

The agency's latest alert includes drugs that contain a potentially carcinogenic "impurity," though no adverse effects related to the recall have been reported.

The FDA said in a statement it was investigating the formation of these impurities, which were reported to be made by mechanisms previously unknown to drug developers.

The factory at the center of the latest recall, Hetero Labs of India, has received warnings from the FDA, and reportedly shredded documents before inspection in 2016.

The Food and Drug Administration has expanded an already widespread recall of common blood pressure and heart failure medications.

The agency's latest alert includes drugs that all contain losartan, in which an "impurity" was found that's been identified as a potential human carcinogen.

N-Nitroso-N-methyl-4-aminobutyric acid or NMBA was identified by the FDA in a news release announcing a voluntary recall by Camber Pharmaceuticals Inc. after it had detected trace amounts of the impurity in the drugs, though the company was not aware of any adverse effects from the recalled batch.

This is the latest of more than 30 blood pressure medicine recalls in the last few years.

As the recalls have continued, the spotlight has shifted to overseas factories in China and India that now produce many drugs that end up in the US.

The lab that produced the most recent batch recalled is Hetero Labs of India.

According to several FDA reports, Hetero employees shredded documents ahead of the scheduled arrival of FDA inspectors in 2016, and did not record what was shredded. In 2017, the FDA issued a warning to Hetero, claiming that the factory did not inspect batch discrepancies, and failed to wash and sanitize their equipment.

According to USA Today, since 2015, the FDA has inspected more foreign factories than domestic ones, but a 2017 Government Accountability Office report found that in mid-2016, nearly 1,000 foreign factories that produce US drugs had gone uninspected. In July 2018, 15% of factory inspector jobs were unfilled.

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Amid the recalls of other ARBs, or angiotensin receptor blockers, medications Commissioner Dr. Scott Gottlieb said in the news release that though consumers face few immediate health threats from the recalls, the agency is "deeply concerned" and pursuing an investigation into the possible presence of a third impurity.

"We are making important strides at understanding how these impurities form and we are continuing to examine if nitrosamine impurities may also arise during the manufacture of other ARB drug products," Gottlieb wrote. "The FDA is committed to implementing measures to prevent the formation of these impurities during drug manufacturing processes in the future."

Maisha Kelly Freeman, a professor and director of Samford University's Center for Healthcare Innovation and Patient Outcomes Research, told CNN that the impurities in the medications were only found after production because the agency wasn't aware of the potential for active ingredients to form a compound that would produce the carcinogen.

The agency said on its site: "Not all ARB products contain NDMA, NDEA or NMBA impurities, so pharmacists may be able to provide an alternative medication not affected by the recalls, or health care professionals may prescribe a different medication that treats the same condition."

Sandy Walsh, a spokesperson for the FDA, told Business Insider the agency uses a "risk-based inspection strategy" to keep an eye on "higher risk facilities" abroad in conjunction with its international regulatory partners in Europe.

"For instance, while surveillance inspections declined slightly in China from 2017-18, inspections in India have increased substantially," Walsh said. "Among other things, the number of inspections in any given country reflects our risk-based prioritization of our inspections and improvements in our targeting; our increasing ability to leverage inspectional work done by trusted partners, especially in Europe; and a higher number of pre-approval inspections."