One of the top advisers to US Vice President Mike Pence tested positive for Covid-19 the day after another member of the White House team was diagnosed with the virus.
Pence's press secretary, Katie Miller, was positive on Friday, the day after President Donald Trump's valet.
The White House initiated daily tests for Pence and Trump, and said it was taking "every precaution to protect the president".
The death toll in the U.S. is now over 76,000 and states are starting to reopen.
Six members of Pence's team were abruptly removed from his Air Force 2 plane after he was kept on the runway outside Washington, DC for more than an hour on Friday, as he prepared to travel to Iowa to find leaders religious.
Team members have had recent contact with Mrs. Miller, according to an unidentified American official cited in the media report. The president and vice president are not.
Miller is the wife of Trump adviser Stephen Miller.
When asked about the possibility of an outbreak at the White House, Trump told reporters, "All you can do is take precautions and do the best you can."
He also said he was right not to wear a mask while visiting the World War II memorial in Washington on VE Day, because the elderly veterans there were with him "away".
"In addition, the wind was blowing so strong and in a direction that, if the plague arrived, I would be very surprised," he added.
On Friday, White House press secretary Kayleigh McEnany defended measures taken by the White House to keep authorities safe.
"We take every precaution to protect the president," said McEnany.
Trump's chief of staff, Mark Meadows, also told reporters, "This is the safest place to go."