At least 14 people have been injured, some seriously, after two cars crashed and ploughed into pedestrians at a car meet in Stevenage.
The accident took place on the A602 in Stevenage, Hertfordshire, on Thursday evening as dozens of people watched "boy racers" take part in the event.
Footage posted on social media showed a car passing another vehicle at speed before they collided and careered off the road.
Hertfordshire Constabulary said two cars were involved in a collision on Monkswood Way at about 9.45pm.
A spokeswoman said: "There were a number of people in the area at the time and 14 people are being treated for injuries, some of which are serious."
Emergency services are expected to remain at the scene for some time.
A witness wrote on Facebook: "Horrific incident in Stevenage. A car (boy racers) has ploughed into at least 10/15 people on the side of a road who were watching on.
"Must be 30+ emergency services on the scene. thoughts are with all involved, looks so bad."
Police have urged any witnesses to get in touch and have asked anyone with footage of the incident to retain it.
The accident happened during a weekly meet of the modified car club Cruise Herts.