CDC head Robert Redfield and FDA chief Stephen Hahn are also quarantining.

Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, will be entering a “modified quarantine” due to exposure to someone who tested positive for the novel coronavirus.

Fauci joins a growing list of administration officials taking precautions following the news of two known coronavirus cases at the White House, including the vice president’s press secretary.

The head of the Centers for Disease Control and Prevention, Director Dr. Robert Redfield, announced Saturday afternoon he would be going into self-quarantine due to “low risk exposure” to someone with the novel coronavirus.

The NIAID said Fauci tested negative for COVID-19 and is considered to be “at relatively low risk based on the degree of his exposure.” Fauci’s quarantine was described as “modified” and he might still go to his office at the National Institutes of Health, where he would be the only one in the building.

“Nevertheless he is taking appropriate precautions to mitigate risk to any of his personal contacts while still allowing him to carry out his responsibilities in this public health crisis,” NIAID told ABC News.

Fauci and Redfield will be entering self-quarantine less than a day after Food and Drug Administration Commissioner Dr. Stephen Hahn said he would be isolating himself for similar reasons.

“CDC Director Dr. Robert Redfield has been determined to have had a low risk exposure on May 6 to a person at the White House who has COVID-19,” the CDC said in a statement. “He is feeling fine, and has no symptoms. He will be teleworking for the next two weeks. In the event Dr. Redfield must go to the White House to fulfill any responsibilities as part of WHTF on COVID-19 he will be following CDC Safety Practices for Critical Infrastructure Workers Who May Have Had Exposure to a Person with Suspected or Confirmed COVID-19.”

“Those guidelines call for Dr. Redfield and anyone working on the Task Force at the WH to have their temperature taken and screened for symptoms each day, wear a face covering, and distance themselves from others,” the agency added.

An FDA spokeswoman confirmed Saturday morning that Hahn also came in contact with an individual who tested positive. As a result of that contact, he was tested but that came back negative.

He is in self-quarantine as well.

“As Dr. Hahn wrote in a note to staff yesterday, he recently came into contact with an individual who has tested positive for COVID-19,” the FDA said in a statement. “Per CDC guidelines, he is now in self-quarantine for the next two weeks. He immediately took a diagnostic test and tested negative for the virus.”

Both men will testify by video — “due to these unusual circumstances” — at Tuesday’s Senate Health Committee hearing about the government response to COVID-19.

“I asked the White House to allow Dr. Hahn and Dr. Redfield to testify by videoconference at this important hearing which is less than three days away,” Chairman Sen. Lamar Alexander, R-Tenn., said in a statement. “I am grateful that White House Chief of Staff, Mark Meadows, approved a one-time exception to the Administration’s policies about hearings, and has agreed that Dr. Hahn and Dr. Redfield will testify at this hearing by videoconference due to these unusual circumstances.”

Fauci was also scheduled to testify at the hearing after the White House rejected a request for him to testify at a House hearing last week.

At this time, Fauci is still expected to show up to the Senate for his testimony on Tuesday, sources told ABC News.

Hahn and Redfield would have regularly come in contact with Vice President Mike Pence and President Donald Trump in consulting with the White House coronavirus task force. Both men have been tested multiple times and come back negative, though it’s unclear if they’ve been tested again this weekend.

Trump said on Friday he would “probably” have another test after a military service member — a personal valet who had brought him Diet Cokes in the Oval Office — had tested positive.

Pence’s press secretary, Katie Miller, who’s married to top Trump policy adviser Stephen Miller, also was revealed to have tested positive for the coronavirus on Friday.

Stephen Miller, one of the president’s closest advisers, tested negative for COVID-19, ABC News has learned.

It is not clear who tested positive for coronavirus and came into contact with Redfield and Hahn.