A 63-year-old man is in hospital with serious injuries after a group of motorcyclists were attacked by a gang of people in four cars on the M74 in South Lanarkshire.
Police Scotland said the "targeted" attack took place between junctions 10 and 11 near Lesmahagow on Sunday.
A red Mazda believed to have been involved in the incident was later recovered in Ayrshire with a smashed rear window.
The other vehicles have not been traced.
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Det Sgt Craig Wait said: "We believe this was a targeted attack on the group of motorcyclists and it's vital we trace the people responsible.
"One man has been seriously injured as a result of the attack and many others, including members of the public who witnessed what happened, have been left shaken.
"I'm appealing to anyone with information to come forward."