A major pile-up involving more than 100 vehicles in misty conditions on the new Sheppey crossing bridge has left eight people seriously injured and 60 suffering minor wounds.
No one is believed to have died in the incident in Kent, which started at around 7.15am and continued for 10 minutes as cars and lorries crashed into each other in visibility that was down to 20 yards.
Witnesses said the accident happened in thick fog, and that some motorists were "driving like idiots".
Police and emergency services were called at 7.15am to the incident, on the London-bound carriageway of the new Sheppey crossing bridge in Kent.
Martin Stammers, 45, from Minster, told Kent Online: "It's horrific. I've never seen anything like it in my life.
"All you could hear was cars crashing. We got out of our car and it was eerily quiet, with visibility down to just 20 yards."
A Kent Police spokeswoman said visibility was a problem over the bridge, but it was not clear whether that caused the pile-up.
"It has been reported there were collisions at the top of the crossing and at the foot of the approach to the crossing," a spokesperson said.
"At this stage it is unknown exactly how many vehicles are involved, but early reports suggest more than 100 vehicles."
Motorists were warned to avoid the area.
"Officers are urging motorists to avoid the area but if a journey to the island is essential, the old Kingsferry Bridge remains open but expect long delays," police said.
"The road remains closed at Cowstead Corner on the island and motorists are being directed on to the Kingsferry Bridge, while the road is closed at the Iwade turn-off and vehicles directed through the village on to the old A249."
The scene on the bridge was a mass of tangled cars, lorries and even a car transporter, with reports saying that the crash went on for 10 minutes as cars continuously collided with each other.
The uninjured and the walking wounded are being taken down from the bridge on the Sittingbourne side.
South East Coast Ambulance Service said it was dealing with a major incident with 30 ambulances and cars at the scene, but a spokesman said he was not aware of any deaths.
It has deployed its hazardous area response teams (HART) to the scene and confirmed there was a wide range of injuries from seriously injured to walking wounded.
"We have set up triage at the scene and are treating patients," he said.
Those injured will be ferried to local hospitals including Medway Maritime Hospital in Gillingham and Queen Elizabeth The Queen Mother Hospital in Margate.
People have been posting shocking pictures of the collision on Twitter, while others have uploaded video to YouTube.