Hillary Clinton left a service at the Sept. 11 memorial in New York City on Sunday early.
According to a statement from Clinton's campaign spokesperson, the candidate felt "overheated," so she went to her daughter's apartment. Clinton is "feeling much better," the statement said.
Fox News, citing an unnamed law enforcement source, said Clinton was having some type of "medical episode." A witness reportedly told the network Clinton's knees "buckled" and she lost a shoe.
The incident comes as Donald Trump has questioned whether she is healthy enough to serve as president. Clinton has said she is healthy and fit to be president.