Police investigating a crash in which two teenagers and a motorist died want to trace a white vehicle seen in the area just before it happened.
The accident on the A66, near Braithwaite in Cumbria, on 24 May involved a car and a coach carrying children home from Keswick School.
Officers believe a white van or lorry may have been in front of the car involved in the collision.
They want the driver, who might have useful information, to get in touch.
It is not thought that the vehicle was involved in the collision.
Kieran Goulding, 15, and Chloe Walker, who was marking her 16th birthday, died. The car driver, Patrick Short, 68, was also killed.
A number of schoolchildren were injured in the incident.
Cumbria Police said the coach was on the correct side of the road when the impact happened.
Early indications were that it swerved to avoid an oncoming car which had crossed the central line and overturned.