The president of Notre Dame university and two more workers at the White House have tested positive for coronavirus, according to reports.
The Rev John Jenkins sent an email to staff to reveal he was infected, days after apologising for not wearing a mask at a Rose Garden event at which Donald Trump unveiled Amy Coney Barrett as his pick for the Supreme Court seat made vacant following the death of Ruth Bader Ginsburg.
"I regret my error of judgement in not wearing a mask," he wrote in the letter.
"I know many of you have read about the White House ceremony I recently attended. I write to express my regret for certain choices I made that day and for failing to lead as I should have," Mr Jenkins said in the letter.
"When I arrived at the White House, a medical professional took me to an exam room to obtain a nasal swab for a rapid Covid-19 test. I was then directed to a room with others, all fully masked, until we were notified that we had all tested negative and were told that it was safe to remove our masks," he wrote. "We were then escorted to the Rose Garden, where I was seated with others who also had just been tested and received negative results."
He said in the email that his symptoms were mild and that he would continue to work from home.
Of the two workers at the White House reported to have tested positive by CNN, one is said to be a journalist and the other a press staffer. The broadcaster did not name either of them.
According to CNN's Brian Stelter, members of the media were being alerted of their potential exposure "so that you can make informed judgements."
The information was detailed in a memo, which also said that "all other journalists tested today tested negative."
The White House Correspondents Associations board issued a statement that said "we can't stress enough the importance of mask wearing, social distancing and common sense, especially on the White House complex."
"Additionally, we are again asking journalists who are not in the pool and do not have an enclosed workspace to refrain from working out of the White House at this time," the board said.
Mr Trump is in isolation and has reported experiencing mild symptoms. His campaign manager, Bill Stepien, said all upcoming campaign events would be postponed or held virtually.
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