Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE left a 9/11 memorial ceremony in New York early on Sunday because she “felt overheated,” her campaign said.

“Secretary Clinton attended the September 11th Commemoration Ceremony for just an hour and thirty minutes this morning to pay her respects and greet some of the families of the fallen,” spokesman Nick Merrill said in a statement.

“During the ceremony, she felt overheated so [she] departed to go to her daughter’s apartment, and is feeling much better,” he said.

As she left her daughter’s apartment late Sunday morning, Clinton said she is “feeling great.”

She added that "it’s a beautiful day in New York," where temperatures were in the low 80s and a breeze was blowing at 10 miles per hour on the 15th anniversary of the Sept. 11, 2001 terrorist attacks. The humidity was approximately 40 percent, according to weather.com.

A law enforcement source told Fox News that Clinton left the ceremony early due to a “medical episode."

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The source said Clinton appeared to faint going into her van.

Fox News reported that Clinton stumbled off a curb and her "knees buckled."

An ABC News staffer tweeted that Clinton aides had not responded to questions about her whereabouts 30 minutes after the incident .

Clinton left the 9/11 ceremony 30+ mins ago but press pool was not told to where. Aides now not responding to any Qs about her whereabouts — Liz Kreutz (@ABCLiz) September 11, 2016

Clinton’s Republican rival, Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE, has repeatedly questioned her health on the campaign trail.

Last week, he criticized the media for not covering a “massive” coughing attack.

"Mainstream media never covered Hillary's massive 'hacking' or coughing attack, yet it is #1 trending," the GOP presidential nominee tweeted Tuesday.

"What's up?"

Trump also said in an interview last week that he would release his full medical records if Clinton makes her records public.

— This breaking news report was last updated at 1:00 p.m.

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Trump, Clinton visit Ground Zero on 9/11 anniversary