Hillary Clinton abruptly left the 9/11 memorial in New York City early on Sunday due to overheating, according to her campaign, fueling rumors that the presidential nominee is seriously ill.

Clinton left after spending an hour and a half at the ceremony, a campaign spokesman wrote in an emailed statement. She then left for her “daughter’s apartment, and is feeling much better.”

Both Donald Trump and Clinton paid tribute to the victims and survivors of the 2001 attacks Sunday morning, when temperatures hit 84 degrees at 11 a.m. Sunday. Clinton left around 9:45 a.m.

According to an unnamed law enforcement source interviewed by right-leaning outlet Fox News, Clinton “stumbled off the curb and appeared to faint” as she got into the van taking her away. Her knees buckled, and she appeared to lose her shoe.

 

The news comes as Trump supporters have recently been pushing a host of theories questioning the Democratic nominee’s physical fitness to lead. Some have suggested that the 68 year old suffers from Parkinson’s disease or a deadly brain clot, while Trump has said Clinton has “no stamina.” A major source of those rumors, a heavily edited clip of Clinton in which she appears to be shaking her head exaggeratedly (and detractors claim to be a seizure), is not backed by Clinton’s medical records.

On Sunday, Clinton was later filmed by MSNBC leaving her daughter, Chelsea Clinton’s apartment around 11:45 a.m. smiling and waving.

Fortune will update this story if there are further developments.