Democratic presidential nominee Hillary Clinton abruptly left a 9/11 memorial ceremony at ground zero in New York Sunday morning.

Initially her campaign reported that she’d become “overheated.” But her doctor later said she had pneumonia and was dehydrated, according to news reports.

Fox 5 in New York reported that a witness had seen Clinton “stumble off a curb” and that her knees buckled.

Fox 5 also reported that she was helped into a van.

A campaign spokesman later issued a statement saying that the 68-year-old Clinton “felt overheated,” went to her daughter Chelsea’s apartment, “and is feeling much better.”

Clinton was later seen coming out of the apartment. She said she was “feeling great.”

Her campaign’s statement said she was attending the ceremony Sunday morning “to pay her respects and greet some of the families of the fallen.”

Both Clinton and GOP presidential nominee Donald Trump had agreed to refrain from public speeches on the 15th anniversary of the Sept. 11, 2001 terrorist attacks.

[Mike Pence Makes Surprise Visit to Pentagon 9/11 Memorial]

Sunday’s incident has already prompted questions about Clinton’s health, and Trump’s as well.

Clinton released a letter more than a year ago from a physician who described her as “a healthy female with hypothyroidism and seasonal allergies.”

“She is in excellent physical condition and fit to serve as president of the United States,” Dr. Lisa Bardack wrote in a letter dated July 28, 2015.

Trump, who at 70 is older than Clinton, has suggested otherwise.

He claimed in a speech last month that she “lacks the mental and physical stamina to take on ISIS and all of the many adversaries we face.”

The Trump campaign also issued a less-detailed doctor’s letter endorsing his fitness to be president last December.

Dr. Jacob Bornstein, who described himself as Trump’s personal physician since 1980, noted that his father also had treated him.

“If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency,” Bornstein wrote in the letter dated Dec. 4, 2015.

It was later reported that Bornstein wrote the letter in five minutes while a limousine sent by Trump waited outside his office.

To date, neither candidate has released their full medical records. But Trump told ABC News earlier this month that he plans to do that.

In an interview with ABC’s David Muir on Monday, Trump said that if Clinton wanted to make her medical history public, he would do the same,”100 percent.”

“Why not go first?” Muir asked.

“I might do that. …. In fact, now that you ask, I think I will do that,” Trump told Muir.