Three men have been arrested on suspicion of dangerous driving after a multi-vehicle crash on the M25.
It happened on the anti-clockwise carriageway between junction nine, near Leatherhead, and junction eight, near Reigate, shortly after midday on Saturday.
One person was taken to hospital for medical treatment, Surrey Police said.
Significant traffic delays are expected, as three of the four lanes were closed. The road was fully reopened shortly after 16:00, National Highways said.