Simon Cowell is in hospital after breaking his back when he fell from his new electric bike.
The X Factor star, 60, was testing the e-bike in the courtyard of his house in Malibu, California, when he fell.
Mr Cowell, who was with his family at the time, hurt his back and was taken to hospital, a spokeswoman said.
He had to have surgery but was “doing fine”, she said.
It is understood that he may have bought the bike as part of an exercise drive after a previous fall in 2017.
He has been pictured on bike rides with his partner, Lauren Silverman, 43, and their six-year-old son, Eric close to their US home in recent months.
“Simon has broken his back and is having surgery this evening,” the star’s spokeswoman said on Saturday.
“Simon had a fall from his bike, testing his new electric bike in the courtyard at his house in Malibu with his family. He hurt his back and was taken to hospital. He’s doing fine, he’s under observation and is in the best possible hands.”
It is understood the surgery started on Saturday evening Los Angeles time.
Mr Cowell’s representatives did not respond to requests for updates on his condition on Sunday. It is unclear if the accident will have any effect on his judging role on America’s Got Talent, which is due to start live shows this week.
The music mogul has claimed in interviews that he has lost 60 pounds in recent years after implementing a diet and exercise regime after falling down the stairs of his Kensington home.
After the accident he told the Sun: “Sometimes we get a reminder that we’re not invincible and this was certainly mine. It was a huge shock.
“They think I fainted because I had low blood pressure and so I have got to really take good care of myself to sort that out.”
He blamed the accident on his “vampire” lifestyle, which saw him staying up until 8am and said that he would change his ways as “I am a dad and have more responsibility than ever.”
After the fall he reportedly bought two 28mph battery-powered bikes worth more than £2,000. He kept one in London and took one to the US with him, it was said. It is understood that he had only just bought the model which he was riding when he fell.
As well as warnings that they do not provide the same level of exercise, there have been safety concerns over the use of electric bikes for those who are not used to them.
When they first became popular in the Netherlands it was warned that more people were being killed every year riding an e-bike than a moped with the elderly at particular risk.
Egbert-Jan van Hasselt, who heads the Dutch police road safety unit, warned: “The e-bike is not a regular bike. It gives you an extra boost, and that sometimes happens unexpectedly. As a result, you can tremble, swing and sometimes even fall.”
Mr Cowell’s accident comes just a month after it emerged that he has bought Sony Music Entertainment’s stake in TV programmes including Britain’s Got Talent and The X Factor.
The move sees the music mogul gain ownership of all the international versions of The X Factor and Got Talent programmes.
The Got Talent format airs in 76 markets, while The X Factor is broadcast in more than 130 territories. Sony Music’s share of the venture has transferred to Syco Entertainment, a company solely owned by Cowell.
Filming on the next stage of this year’s Britain’s Got Talent has been postponed because of the coronavirus crisis but ITV has said it hopes to continue the series later this year.