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Part of the M20 had to be closed in the early hours of this morning after a person was seen on the wrong side of the railings on a bridge overhead.
Kent Police was called at 12.30am after the youth was spotted near Junction 2 at Wrotham.
Both carriageways were closed while emergency services dealt with the incident.
A police spokesman said: "The person, a teenage boy, was detained under the Mental Health Act. He was not injured in the incident."
The road was reopened around 2.30am.