Health Canada has paused a plan to distribute the first 300,000 doses of the Johnson & Johnson vaccine after learning the shots are connected to a Maryland plant that is under scrutiny from U.S. officials over over unsanitary conditions and quality control issues.

On Friday, federal regulators said in a statement that the vaccine doses are being reviewed to ensure they are high quality. The doses were manufactured by Baltimore-based Emergent BioSolutions, which spoiled 15 million Johnson & Johnson shots in March due to a production error.

Health Canada previously gave a green light to 1.5 million shots of the AstraZeneca vaccine made at the same plant. Since then, the agency said it has learned “that a drug substance produced at the Emergent site was used in the manufacturing” of Canada’s Johnson & Johnson shipment.

“As with all vaccines imported into Canada, the Janssen vaccines will only be released for distribution once Health Canada is satisfied that they meet the Department’s high standards for quality, safety and efficacy,” the statement reads. “Health Canada has rigorous processes in place to continually monitor the quality of vaccines that are administered to Canadians.

The Johnson & Johnson vaccine was not factored into Ontario’s recently accelerated vaccination timeline. The shots arrived in Canada on Wednesday are being held in a storage facility near Pearson Airport.

Emergent is now the subject of a lawsuit from investors accusing executives of inflating the company’s stock price and covering up problems at the Baltimore plant.