Police called to people climbing up structure close to junction 30 of M25.
Essex Police says officers are on the scene and have made arrests in connection with the incident.
The force says officers are working to keep disruption to a minimum.
A spokesman for Essex Police said: "We are currently responding to reports of people climbing up on an overhead gantry close to Junction 30 of the M25.
"Officers are on the scene and working to keep disruption to a minimum to keep Essex moving this morning. Arrests have already been made by our officers at a number of locations.
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"The operational team in charge of this response have acted quickly and ask the public not to intervene.
"These arrests have formed part of a nationwide operational response to protest activity. The Metropolitan Police Service arrested a number of people for their involvement in planned motorway protest activity."
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