Police in Hampshire are appealing for information after a teenager was found with serious injuries in a live lane on the M27.
Officers were called to the westbound carriageway between junctions 5 and 7 just after midnight on Sunday morning.
A 17-year-old boy was found in the road with serious injuries, police said.
Hampshire Police said enquiries are being made into how the boy came to be on the motorway and how he sustained the injuries.
No further information on the nature of the teenager's injuries has been released.
The westbound carriageway between junctions 7 and 5 and the overhead Botley Road bridge have also been closed.
The closures were likely to remain in place for a few hours, police said.
The force is appealing to anyone who saw any pedestrians in the area of the motorway during the early hours of Sunday.
They’re also asking if anyone saw pedestrians on the Botley Road bridge, which runs overhead.
The force said: "Were you walking along the motorway at this time? Were you with this person or did you see them? Please be reassured that you are not in any trouble, we are seeking any witnesses who can help us establish what happened."
Anyone with information is asked to contact police on 101, quoting incident 24 of today’s date or contact Cimestoppers 100% anonymously on 0800 555 111.
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