Hillary Clinton has cancelled a two-day trip to California starting from Monday after the Democratic presidential candidate was diagnosed with pneumonia and has been advised to rest by her doctor.
The cancellation was confirmed by her campaign on Sunday night following Clinton's abrupt departure from a ceremony marking the 15th anniversary of the September 11 attacks in downtown Manhattan because she felt "overheated", The Hill daily reported.
She was supposed to campaign in San Francisco and Los Angeles and was scheduled to make an appearance on The Ellen DeGeneres Show.
The former secretary of state's doctor, Lisa R Bardack released a statement revealing the diagnosis on Sunday evening, The Hill daily reported.
Bardack said Clinton had an examination at her home in Chappaqua after the incident, which was a result of dehydration and overheating.
She said the presidential candidate was "re-hydrated and recovering nicely".
Clinton left the Ground Zero ceremony after an hour and thirty minutes.
Video posted by a bystander to Twitter appeared to show Clinton extremely unsteady and supported by aides, being helped from the curb into a vehicle.
A security official told the Guardian that Clinton had walked from the ceremony without support, got into a vehicle and was away.
Clinton recently sustained a coughing attack during a campaign event in Cleveland, fuelling suspicion about her health and leading to the creation of a hashtag, #HackingHillary.
Republican rival Donald Trump using the hashtag tweeted: "Mainstream media never covered Hillary's massive 'hacking' or coughing attack, yet it is #1 trending. What's up?" the Guardian added.
Rumours about Clinton's health appeared to have stemmed from a 2012 incident in which she fell, a mishap attributed to a stomach virus.
She suffered a concussion and a subsequent blood clot in the brain, which later testing showed to have cleared completely.