Lausanne (AFP) - Former world champion Fabian Cancellara could be investigated over accusations that he used a hidden motor in his bicycle, world governing body the UCI told AFP on Thursday.

"We can't rule out opening an investigation if new elements come into our possession," a UCI spokesman said, confirming comments also made by UCI president David Lappartient to the Cyclingnews website.

"We need to know exactly what is behind this. Of course, I heard all the rumours, like everybody, and I just want to know exactly. So we will investigate, that is our job," Lappartient said.

"I hope that this (mechanical doping) never happened in professional cycling. If this was the case, it would be a disaster for the image of cycling and that's why we have to fight."

Lappartient was reacting to accusations made against Swiss star Cancellara by former cyclist Phil Gaimon in a new book.

"When you watch the footage, his accelerations don't look natural at all, like he's having trouble staying on the top of the pedals," American rider Gaimon wrote.

Cancellara, who quit the sport in 2016, faced accusations that he was using a hidden motor following his wins at the 2010 Tour of Flanders and Paris-Roubaix.

Cancellara has always denied the allegations.