The incident saw England’s Matt Walls sent over the corner barriers and into spectators, while the multi-rider crash saw all but six riders pile up on the inside of the track.
The 24-year-old received medical attention for 40 minutes, before being taken away by an ambulance.
Cyclists were competing in the second men’s scratch qualification heats when Canadian Mathias Guillemette caused the contact which initiated the crash.
Australia’s Josh Duffy was sent sliding up the banking, forcing Walls wider into, and eventually over, the barriers to avoid colliding with other racers.
The Englishman collided into the front row of spectators, who witnesses say were unsighted due to the gradient of the track.
Canadian Derek Gee also slid across the top of the barrier, but managed to fall back into the track.
Isle of Man’s Matt Bostock was also taken to hospital after sustaining head and shoulder injuries.
Guillemette was disqualified from the race.
A male spectator was treated for cuts to his arm, whilst a girl received minor medical attention.
The remainder of the morning session was cancelled, with fans asked to leave the Velodrome so medical staff could see to Walls.
British Cycling released a statement, which read: “Following a crash in the men’s scratch, Matt Walls and Matt Bostock are being treated by medics before being taken to hospital for further treatment.
“We send our best wishes to the riders and spectators involved in the incident, and will provide a further update when we can.”
We echo their thoughts and can only hope all involved are OK!