The M1 motorway has been closed in both directions near Northampton after police were called to an incident.
A spokesman for Northamptonshire Police said officers were called to a bridge over the motorway between junctions 15 and 15A to help “a person in crisis”.
Traffic has come to a standstill in both directions and motorists have been urged to remain patient and avoid the area if possible.
The incident began at 1345 BST and is ongoing.
Insp Carl Sturman of Northamptonshire Police said: “We are dealing with a person in crisis on a bridge.
“We have police-trained negotiators at the scene and we’re trying to resolve this incident as swiftly and safely as possible for all people involved.
“We ask members of the public to please bear with us and be patient.”
The Highways Agency said a diversion route had been set up for southbound traffic.
It should leave the M1 at junction 15A, follow the black hollow triangle diversion symbol, and re-join the motorway at junction 15.
The diversion route for northbound traffic has yet to be confirmed.
A Highways Agency spokesman said there were long delays in both directions on the approach to the scene.
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