La Mondiale team riders including Jan Bakelants and Romain Bardet in action. Christian Hartmann/Reuters

Thermal cameras aimed at catching out technological cheats will again be used at the Tour de France this year, the French Sports Ministry said on Saturday as the world's biggest bike race began in Dusseldorf.

Cycling's world governing body the UCI will carry out unannounced checks on riders' bicycles using technology developed by the French Alternative Energies and Atomic Energy Commission (CEA).

The technology was first used at the Tour last year when no bikes failed a test.

That Tour was also noticeable for there being no devastating performances that could have aroused suspicion, unlike some from previous years.

Authorities had decided to clamp down on technological fraud last season after years of rumours that some riders might be using motorised bicycles.

To date only one such bike has been found at an official race, when Belgian teenager Femke Van den Driessche was caught with a motorised bicycle at the Cyclo-cross World Championships 18 months ago.

She was subsequently banned for six years.

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