The mangled wrecks of cars and lorries were strewn across the Sheppey Crossing as vehicles smashed into each other in a series of collisions at about 7.20 a.m. (0630 GMT).
“All we could hear was screeching, cars thudding into each other, lorries crashing,” driver Martin Stammers told the BBC.
Firefighters cut six people from their vehicles and 35 were taken to hospital, eight with serious injuries.
Witnesses said there was thick fog at the Crossing, a road bridge which links the Isle of Sheppey in the mouth of the River Thames estuary to the mainland about 50 miles east of London.
Police said they were still investigating the cause of the accident.
(Reporting by Michael Holden; Editing by Andrew Heavens)