BAFFLED TV viewers have struggled to explain a mysterious object hidden under Hillary Clinton's jacket during Monday's presidential debate.

The Democrat candidate appeared to have a box attached to her back with a wire running upwards.

4 TV viewers were at a loss to explain a mysterious box-shaped lump and apparent wire underneath Hillary Clinton's jacket on Monday night

4 Donald Trump and Clinton sparred during the first TV debate on Monday evening Credit: Reuters

And eagle-eyed viewers also noticed a see-through ear piece planted in Clinton's ear during her verbal sparring match with Republican Donald Trump.

Conspiracy theorists quickly raced to explain what the mysterious object was.

It was soon pointed out that rival Trump was not sporting a similarly-sized box.

In one bizarre theory, it was suggested the device was used to allaywas wearing

A second theory suggested it was an inductive earpiece - used to hit certain cues within a speech.

And thirdly, one suggested it was an anti-seizure device, used to warn of an impending collapse.

Clinton collapsed earlier this month after being forced to leave a 9/11 memorial early.

The former First Lady was walked to a waiting convoy of cars by her security team where her legs appeared to give way.

Clinton, 68, was whisked to her daughter Chelsea's home before making an appearance outside later on to declare she was fighting fit.

She was later diagnosed with pneumonia.

Trump appeared to used the episode as a tool to question his rival's "stamina".

He said: "She doesn't have the look. She doesn't have the stamina, I said she doesn't have the stamina, and I