A 20-year-old woman has died after the "Boris Bike" she was riding was in collision with a lorry.
The accident happened in Whitechapel High Street in east London on Friday evening.
Transport for London (TfL) said it is the first fatality involving one of the hire bikes, dubbed Boris Bikes after being launched by London Mayor Boris Johnson in 2010.
Leon Daniels, TfL's managing director of surface transport, said: "Our thoughts go out to the friends and family of the female cyclist who tragically died ... following a collision with a heavy goods vehicle on Whitechapel High Street. We understand she was riding a Barclays Cycle Hire bike.
"TfL has a range of measures already under way to further reduce the number of collisions involving cyclists across London and we will be assisting the Metropolitan Police with their investigation into this tragic incident."
The accident is believed to have occurred on Cycle Superhighway 2 outside Aldgate East underground station. The Barclays cycle routes run from outer London to the centre and are designed to provide "safer, faster and more direct journeys into the city", according to TfL.
Four have been opened so far, with a further eight to be introduced by 2015.
A Metropolitan Police spokesman said traffic officers are appealing for witnesses to the collision which occurred just before 6.20pm. The HGV driver, who stopped at the scene, was not arrested.
London Ambulance Service took the woman to Royal London Hospital where she was later pronounced dead. Her next of kin have yet to be informed.
Officers from the road death investigation unit at Chadwell Heath traffic garage are investigating the circumstances of the collision. Any witnesses are asked to call police on 0208 597 4874.