The White House and the director of the Centers for Disease Control and Prevention were engaged in a tense standoff on Thursday after Health Secretary Robert F. Kennedy Jr. tried to fire the director, Susan Monarez, and multiple high-ranking agency officials resigned.

The White House said that she had been dismissed. But her lawyers, who said she had chosen “protecting the public over serving a political agenda,” insisted that she remained C.D.C. director until President Trump fired her personally.

The dispute now appears to be in the hands of Mr. Trump, who has not weighed in publicly. A spokesman for the White House did not respond to an inquiry about whether the president would fire Dr. Monarez.

The Republican-led Senate voted only last month to confirm her; she is the first C.D.C. director to be subject to Senate confirmation. As such, she works at the pleasure of the president, not Mr. Kennedy.

Senators from both parties expressed dismay at the events unfolding at the C.D.C.

The chairman of the Senate health committee, Senator Bill Cassidy, a Louisiana Republican and physician who voted for Mr. Kennedy, said on social media late Wednesday that the “high profile departures will require oversight” by his panel. He did not elaborate.

Senator Bernie Sanders, the Vermont independent and ranking member of the panel, called for a hearing with Mr. Kennedy and Dr. Monarez and said the attempt to fire her was “outrageous.”