Police want to trace the drivers of three vehicles that were yards away from a car and a bus that crashed on the A259 in Seaford.
A white Toyota Yaris and a Brighton and Hove bus were both in Newhaven Road travelling towards Newhaven when they collided at 2.50pm on Tuesday (May 27).
The driver of the bus, a 67-year-old from Seaford, and six passengers were all treated for minor injuries.
Two 42-year-old men from Newhaven who were passengers in the Toyota were taken to Royal Sussex County Hospital after breaking their necks in the collision.
The other Toyota passenger, a 17-year-old from Newhaven, received a minor injury. The driver, an 18-year-old from Newhaven, was not injured.
Officers are keen to speak to the driver of a silver Vauxhall Corsa that was travelling eastbound towards Seaford behind another Brighton and Hove bus, the driver of a blue Vauxhall Insignia estate that was in front of the white Toyota Yaris and the driver of a dark Mercedes convertible that was behind the double decker bus when the crash happened.
PC Richard Hobbs said: “The drivers must have seen the crash happen and I am keen to speak to them to see what they know.
“It was a busy time of day and I would also like to speak to anyone else who was in the area and who saw what happened.”
Anyone with information should call 101 quoting serial 803 of 27/5 or email firstname.lastname@example.org.