The commissioner of the US Food and Drug Administration on Sunday urged Americans observing Memorial Day weekend to follow federal guidelines aimed at curbing the spread of the coronavirus, saying the deadly virus “is not yet contained.”

“With the country starting to open up this holiday weekend, I again remind everyone that the coronavirus is not yet contained. It is up to every individual to protect themselves and their community. Social distancing, hand washing and wearing masks protect us all,” Dr. Stephen Hahn wrote in a tweet.

The commissioner’s Memorial Day warning comes as some states begin to reopen, allowing people to go to beaches, cookouts and bars as they observe one of the more popular holidays that’s to take place amid the pandemic. But as social activities increase, health experts like Hahn warn the US is still not out of the woods.

“Even as states and some state officials rush to reopen it’s on us to make smart and safe decisions,” Dr. Seema Yasmin, a former disease detective at the US Centers for Disease Control and Prevention, told CNN Saturday night.

Dr. Anthony Fauci, the nation’s top infectious disease expert, told the public last week that going outside was fine, with cautious measures.

“Go out, wear a mask, stay 6 feet away from anyone so you can have the physical distancing,” he told a CNN coronavirus town hall. “Go for a run. Go for a walk. Go fishing. As long as you’re not in a crowd and you’re not in a situation where you can physically transmit the virus.”

Hahn’s Sunday warning also comes a day before President Donald Trump is set to take a trip to Baltimore that the city’s mayor has recommended against due to the stay-at-home orders the city is continuing to ask its residents to observe.

Hahn repeatedly pledged in a CNN interview last week that science and data would be his “north star” while leading the FDA through the pandemic. Then, a few hours later, Trump went on national television and politicized medical research and brazenly flouted FDA warnings.

That back-and-forth with the President continued this weekend with Hahn sending his warning as Trump tweeted at him about hydroxychloroquine, a drug the President has promoted while the FDA chief has stressed the need for a “large, pragmatic clinical trial.”

Dr. Scott Gottlieb, a former FDA commissioner who served under Trump, told CBS on Sunday that “elected leaders should be setting a strong example on what kind of behavior we should engage in” when asked whether Trump and Vice President Mike Pence’s public messaging is dangerous.

“Because if we do engage in that careful behavior, if we’re more careful in what we do, I think that’s actually going to facilitate a successful reopening and getting back to the important things, getting back to the economic activity,” he said.