NEW YORK – Hillary Clinton has been suffering from pneumonia, her doctor said Sunday, hours after the Democratic nominee abruptly left a 9/11 memorial service in New York City because she “felt overheated.”

On Friday, Clinton was diagnosed with pneumonia, and “put on antibiotics, and advised to rest and modify her schedule,” her physician, Dr. Lisa Bardack, said in a statement.

“While at this morning’s event, she became overheated and dehydrated. I have just examined her and she is now rehydrated and recovering nicely,” Dr. Bardack, chairman of internal medicine at the Mount Kisco Medical Group.

Earlier, her campaign said Clinton was overcome attending a September 11 Commemoration Ceremony for 90 minutes. “During the ceremony, she felt overheated so departed to go to her daughter’s apartment, and is feeling much better,” Clinton campaign spokesman Nick Merrill said in a statement.

A senior law enforcement official told CNN that Clinton came to the ceremony not feeling well, but said she wanted to be there to pay her respects to the victims and families of the 9/11 terrorist attacks.

A video of Clinton’s departure from the event, posted by Twitter user Zdenek Gazda, appears to show her stumbling and being helped into a waiting van.

Clinton left her daughter’s apartment before noon, saying “I’m feeling great, it’s a beautiful day in New York.”

The former secretary of state then went to her home in Chappaqua, a New York suburb, where she was attended to by Dr. Bardack.

In Cleveland last week, Clinton suffered a two-minute coughing fit last week, which she blamed on allergies.

Congressman Joe Crowley, a Democrat, who stood next to Clinton during the ceremony, told NBC, “It was very hot and stifling, very tight, inches from each other … like typically would be at a ceremony like this.”

The high in lower Manhattan was expected to reach 83 degrees Sunday, according to The Weather Channel.

Clinton and her campaign have dismissed recent rumors of ill health. Trump issued her a challenge, in an August tweet, to release her medical records. On Sunday, Trump made no mention of Clinton’s medical situation on Twitter.

The commemoration ceremony at the 9/11 Memorial did not include any public officials speaking. Before the ceremony, however, Clinton spoke, saying “We’ll never forget the horror of September 11, 2001. Let’s honour the lives and the tremendous spirit of the victims and responders.”