By Nigel Wynn
— Zona Cycling (@zonacycling) May 1, 2016
A stalled race motorcycle caused a huge crash in the peloton just after the start of the Red Hook Criterium in New York, USA, on Saturday.
The footage - widely shared on social media - shows the motorcycle leading the race and then coming to an abrupt stop in the middle of the road.
Several of the leading riders manage to swerve around the motorcycle, although there is not a great deal of room to pass between the barriers at the side of the road.
As soon as one rider hits the back of the motorcycle, it causes a huge pile-up with riders hitting fallen riders and bicycles at speed.
On-bike footage posted on Instagram and YouTube gives a rider's-eye view of the incident, apparently filmed by Antoine Fabry.
The Red Hook Criterium features riders competing on fixed wheel bikes around a short and technical circuit. There are four races in the series, in Brooklyn, London, Barcelona and Milan.
Race motorcycles have been involved in a string of incidents this season, with an increasing amount of calls to regulate their use to prevent crashes and injuries. Belgian rider Antoine Demoitié (Wanty Groupe Gobert) died after colliding with a race motorcycle during Ghent-Wevelgem.
Stig Broeckx (Lotto-Soudal) broke his collarbone after hitting a motorcycle during Kuurne-Brussels-Kuurne and Elia Viviani (Sky) crashed after colliding with a moto at Paris-Roubaix.