Hillary Clinton leaves a memorial service at the National 9/11 Memorial in New York after feeling "overheated." | Getty Clinton abruptly departs 9/11 memorial service after feeling 'overheated' She emerged from her daughter’s apartment hours later to say she was ‘feeling great.'

NEW YORK — Hillary Clinton left the 9/11 memorial ceremony early on Sunday after feeling "overheated," her campaign said.

Clinton left the viewing area around 9:30 a.m., just over an hour after arriving, and went to her daughter Chelsea Clinton’s apartment, according to spokesman Nick Merrill, who added she “is feeling much better."


Clinton smiled and waved as she left the apartment building around 11:45, headed to her home in Chappaqua, according to the campaign. "I'm feeling great, it's a beautiful day in New York," she said, greeted briefly by a small girl who approached her on the street.

Earlier in the morning, news reports had circulated that Clinton had left due to a medical episode and was driven away early. It was later revealed that Clinton had been diagnosed with pneumonia late last week.

Video posted on Twitter shows a woman that appears to be Clinton briefly swooning before being helped into a waiting van by her staff. POLITICO has asked the campaign to confirm the clip's authenticity.

Hillary Clinton 9/11 NYC pic.twitter.com/q9YnsjTxss — Zdenek Gazda (@zgazda66) September 11, 2016

Because the event was a small, non-campaign event, just a small pool of reporters was there to cover the ceremony, but those on hand did not witness any incident. Calls and emails to more than a dozen Clinton staffers and associates asking for explanation were not returned.

Donald Trump was also in attendance at the event marking 15 years since the terrorist attacks, remaining until later in the morning.

Temperatures on Sunday morning in New York hovered around 80 degrees most of the morning. At the start of the ceremony, the dew point was around 72 degrees — which produces oppressive humidity, according to meteorologists. The humidity declined sharply during the ceremony, and by 11 a.m., the air was drier and pleasant.

Sen. Chuck Schumer of New York, who attended the ceremony with Clinton, said he chatted with her for "quite a while" about their families and 9/11 memories.

"It was pretty hot out there, but she seemed fine to me, and left on her own accord," Schumer said in a statement on Sunday afternoon.

Clinton’s health has been an issue in the campaign for months, and Trump alluded to the speculation as recently as last week.

"Mainstream media never covered Hillary’s massive 'hacking' or coughing attack, yet it is #1 trending. What’s up?" he tweeted on Tuesday. (Aides said that Clinton, who coughed several times during a campaign event Monday in Ohio, suffers from seasonal allergies. "I've been talking so much," Clinton joked at the time. "Every time I think about Trump, I get allergic.")

Trump supporters have actively fanned rumors about her health, in some cases circulating false medical letters purporting to be from her doctor.

Clinton’s camp felt compelled to respond in mid-August, releasing a statement from her physician, Dr. Lisa Bardack, proclaiming Clinton’s “excellent health” while recirculating a letter describing her health in greater detail.

“To reiterate what I said in my previous statement, Secretary Clinton is in excellent health and fit to serve as President of the United States,” Bardack said last month.

Clinton, who is 68, has always dismissed health questions when asked about them, and her campaign called speculation in the conservative media "deranged conspiracy theories."

Hillary Clinton waves after leaving her daughter's apartment on Sept. 11 in New York. Clinton left the 9/11 anniversary ceremony in New York early after feeling "overheated." | AP Photo

In late August, Clinton addressed the claims on Jimmy Kimmel’s talk show.

“Back in October, the National Enquirer said I would be dead in six months. So with every breath I take I feel like I have a new lease on life,” she said. “I don’t know why they are saying this. I think on the one hand, it is part of the wacky strategy — just say all these crazy things and maybe you can get some people to believe you."

Much of the whispering about Clinton’s health stems from her December 2012 concussion and ensuing blood clot during the closing days of her tenure at the State Department. The conversation re-ignited in recent days after FBI records showed she said she could not recall every briefing she received.

Bardack's letter, released in July 2015, described the aftereffects of Clinton's concussion in some detail.

“In December of 2012, Mrs. Clinton suffered a stomach virus after traveling, became dehydrated, fainted and sustained a concussion,” Bardack wrote. The concussion temporarily prevented Clinton from testifying before congressional commitees over the Sept. 11, 2012, attacks in Benghazi, Libya.

Clinton was prescribed blood thinners to treat “transverse sinus thrombosis,” and she suffered briefly from double vision. For about two months, she wore special glasses as a result, but a visit to Bardack in 2013 found “complete resolution of the effects of the concussion as well as total dissolution of the thrombosis."

Her campaign has sought to turn questions about Clinton's health back on Trump, mocking the speculation as "idiotic" — in the words of her running mate, Tim Kaine — and demanding that the 70-year-old Republican nominee release his medical records in full.

On Aug. 28, Trump tweeted: "I think that both candidates, Crooked Hillary and myself, should release detailed medical records. I have no problem in doing so! Hillary?"

Steve Shepard and Burgess Everett contributed from Washington.