An alleged worker mistake at a pharmaceutical plant that is helping to produce and distribute vaccines by Astra Zeneca and Johnson & Johnson led to the contamination of millions of doses, the Financial Times reports.

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The plant will now supply Johnson & Johnson vaccines exclusively, while Astra Zeneca will set up a new facility in another location.

J&J said in a statement it is “assuming full responsibility regarding the manufacturing of drug substance for its COVID-19 vaccine at the Emergent BioSolutions Inc. Bayview facility.”

The company is adding new workers in operations and quality management for the drug, and it’s increasing the number of manufacturing, quality and technical operations personnel to work at the plant, according to the statement.

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The New York Times reported that the error happened last week when workers at the Baltimore, Md. facility mixed substances for the AstraZeneca vaccine into substances for the J&J vaccine.

The mistake is thought to have ruined nearly 15 million doses of vaccine from both companies. As of Wednesday morning, the Times reports that an estimated 62 million doses must now be checked for contamination.

The plant has produced roughly 150 million doses of the vaccine, but none of them have yet reached the arms of the public. Regulators have not yet certified the factory to allow the vaccines to be distributed to the public, the Times adds.

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This is not the first time vaccines from the Emergent plant have been thrown out. From late 2020 until January 2021, Emergent discarded anywhere from 10-15 million doses of the AstraZeneca vaccine because of “contamination or suspected contamination,” according to the Times. The information comes from internal logs, a government official and a former company supervisor.

The Times adds that previously undisclosed internal documents and interviews with federal officials depict a “factory operation that was ill-equipped to take on such a mammoth manufacturing task.”

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Emergent CEO Robert Kramer denies the claims that workers mixed ingredients, although he has not offered details as to why the batch failed to meet quality specifications, BioPharmaDive reports.

In an interview with CNBC on April 1, Kramer said, “It wasn’t the case where an ingredient from one vaccine contaminated or impacted the other. It was more simply the fact that one production run, one batch of product, was determined to be inconsistent with our quality specifications of Emergent and J&J.”

J&J will now take control over the manufacturing processes at the plant, and with increased J&J personnel, the company claims to be on track to deliver 100 million doses by the end of May.

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This article originally appeared on GOBankingRates.com: Workers Ruin 15 Million Vaccine Doses, J&J Scrambles to Fix Mistake