The Trump administration has instructed federal health agencies to pause all external communications, such as health advisories, weekly scientific reports, updates to websites and social media posts, according to nearly a dozen current and former officials and other people familiar with the matter.

The instructions were delivered Tuesday to staff at agencies inside the Department of Health and Human Services, including officials at the Food and Drug Administration, the Centers for Disease Control and Prevention and National Institutes of Health, one day after the new administration took office, according to the people with knowledge, who spoke on the condition of anonymity to describe private conversations. Some people familiar with the matter acknowledged that they expected some review during a presidential transition but said they were confused by the pause’s scope and indeterminate length.