President didn't disclose 1st positive test, sources say

With little warning, President Donald Trump left Walter Reed Hospital for a few minutes in his motorcade Sunday evening to greet supporters who were outside.

Trump, appearing with a mask from the window of his vehicle, was seen waving to a crowd.

The president tweeted a video before the drive-by appearance thanking his supporters and saying he was going to "make a little surprise visit."

Trump also said in the video that he visited soldiers and first responders at the hospital.

It was not immediately known if there was anyone else in the car aside from the driver. A Secret Service spokesperson declined to comment on the impact of Trump’s trip on the health and safety of their agents, saying they "do not comment on presidential protection."

A senior administration official told ABC News afterward that Trump had returned to the hospital and that he had not been discharged.

Administration member Judd Deere subsequently put out a statement saying that, "President Trump took a short, last-minute motorcade ride to wave to his supporters outside and has now returned to the Presidential Suite inside Walter Reed."

There have been no updates on Trump's condition from his physicians since earlier in the day, when they told reporters he could be released as early as Monday.

-ABC News' John Santucci, Justin Fishel, Elizabeth Thomas and Jack Date

President Donald Trump posted on Twitter Sunday afternoon that he appreciates "all of the fans and supporters outside of the hospital."

The medical team treating the president is hopeful that he will be discharged from Walter Reed Medical Center on Monday.

The New Jersey Health Department tweeted out an update Sunday about the people who attended an event with President Trump at the Trump National Golf Course in Bedminster, New Jersey, last week, shortly before the president and other administration officials tested positive for COVID-19.

It was initially reported that about 100 guests attended the event, but the list the White House sent to the Health Department included the names of 206 people who attended events with those later determined to be infected with the coronavirus.

"DOH has reached out to these individuals to make them aware of possible exposure and recommend that they self-monitor for symptoms and quarantine if they were in close contact with the President and his staff," the health department tweeted.

Health officials are currently interviewing the club’s staff members, all of whom live in Somerset County, and providing health recommendations. The Health Department has begun contract tracing for those guests, and urging any concerned members to quarantine for 14 days.

"Attendees that are seeking a test should consider waiting at least 5-7 days from the event. While the risk is low, a negative test earlier than that time cannot definitively rule out that COVID-19 will not develop," the agency tweeted.

A spokeswoman for the Department of Justice told reporters on Sunday that Attorney General Bill Barr took "two rapid tests and one pcr test since Friday morning." All of the tests came back negative, according to DOJ spokeswoman Kerri Kupec.

"Out of an abundance of caution, he went to the department for only one meeting on Friday, stayed home this weekend other than getting tested, and will stay home tomorrow," she said.

A DOJ official also told ABC News that Barr is postponing a planned trip to St. Louis this week, which was supposed to be a part of the department’s “Operation Legend” initiative.

Barr attended the Sept. 26 event at the White House where President Trump announced Judge Amy Coney Barrett as his Supreme Court Justice nominee.

Several Trump administration officials who contracted the virus last week, including Kellyanne Conway and former Gov. Chris Christie, attended the event and were not wearing masks during the outdoor ceremony.

Barr was photographed talking with Conway and not wearing a mask during the event.

-ABC News' Alexander Mallin