Susan Boyle has sparked concern for her mental health following a bizarre incident at London's Heathrow airport in London.

On Tuesday, as the 48-year-old singer was preparing to board a plane to Chicago she grabbed a mop from a cleaner sung into it used it to clean fellow passengers' shoes, according to The Sun newspaper.

British Airways staff tried to calm the former Britain's Got Talent star down, but she apparently ran off shouting: "I've escaped, I've escaped!"

"It was chaos. Susan was very restless and agitated from the minute she walked in and immediately started making a scene,” a source said.

"She was singing and dancing around, shouting obscenities at full volume."

The incident is thought to have triggered complaints from a number of passengers.

A British Airways spokesperson said: "A customer in the BA lounge on Tuesday was asked to temper their behaviour as it was becoming disruptive.”

Susan was travelling to the US to pre-record a performance on The Oprah Winfrey show, which is due to air net week.

The singer was treated for exhaustion last year following her appearance on Britain's Got Talent.