Emergent BioSolutions has shut down new manufacturing of Johnson & Johnson’s coronavirus vaccine at its Baltimore plant at the request of the Food and Drug Administration after an inspection of the troubled facility last week, Emergent said Monday.

The halt in production is another setback for Johnson & Johnson as it attempts to meet its promise to deliver nearly 100 million doses of vaccine to the U.S. government by the end of May.

Emergent’s brief statement Monday said the FDA began a new inspection of its Bayview facility on April 12. On Friday, at the FDA’s request, “Emergent agreed not to initiate the manufacturing of any new material at its Bayview facility and to quarantine existing material manufactured at the Bayview facility pending completion of the inspection and remediation of any resulting findings,’’ the company said.

It said it was striving to make unspecified improvements “to meet the high standards we have set for ourselves and to restore confidence in our quality systems and manufacturing processes.”

Emergent’s stock price sank 12.6 percent to $67.87 per share by the close of trading. The biodefense contractor won hundreds of millions of dollars in government contracts and vaccine work last year, and investors had pushed its stock price to $125 per share in February.

Some countries were struggling to speed up immunization drives when news of rare side effects associated with the Johnson & Johnson vaccine first emerged. (The Washington Post)

Contamination with ingredients from a coronavirus vaccine made by AstraZeneca ruined 15 million doses of Johnson & Johnson’s vaccine last month. In response to that error, the Biden administration removed AstraZeneca manufacturing from the plant and put Johnson & Johnson in direct control of vaccine production there.

AstraZeneca and Johnson & Johnson have not disclosed how many doses of vaccine have previously been shipped from the Emergent plant and put into vials by other manufacturers.

The quarantine of packaged vaccine could delay millions of doses further down the distribution pipeline. But none of those doses have yet been administered in the United States, U.S. officials have said.

Emergent’s manufacturing of Johnson & Johnson vaccine has not been certified by the FDA, so vaccines made there cannot be used. Johnson & Johnson has been forced to turn to imported vaccine produced in the Netherlands for early supplies of shots for American arms.

AstraZeneca vaccine has not been approved for emergency use in the United States, although the Biden administration has sent a few million doses to Mexico and Canada.

The latest development could create further delays for Johnson & Johnson vaccine manufacturing. Johnson & Johnson had already backed off its previous pledge to produce 24 million new doses of its vaccine at Emergent by the end of April. Its federal contract calls for it to deliver 100 million doses of vaccine. The Biden administration has touted the single-shot vaccine as part of its plan to help return the United States to a sense of normalcy during the summer.

Johnson & Johnson said it’s working to resolve the situation at Emergent.

“We will work with Emergent and FDA to address any findings at the conclusion of the FDA inspection,’’ said company spokesman Jake Sargent in a statement. “At this time, it is premature to speculate on any potential impact this could have on the timing of our vaccine deliveries. We remain committed to delivering 100 million single-shot doses of our coronavirus vaccine to the U.S. Government and helping to bring an end to this global pandemic.’’

Johnson & Johnson has an agreement with Merck, brokered by the Biden administration, for vaccine manufacturing, but it is not expected to produce raw vaccine substance for months.

A federal official who spoke on the condition of anonymity to discuss ongoing federal reviews said Emergent would be notified later this week on the inspection results.

“We recognize the confusion these recent events may have caused our customers, our employees, and the public,” Emergent said in its statement.

The administering of Johnson & Johnson’s vaccine has been put on pause in the United States because of the potential for rare, life-threatening blood clots.