An incident on the M1 between Junction 6 and Junction 5 led to the motorway being closed on both sides from around 12.45am.
Hertfordshire Police attended the scene, along with other emergency services and, at 3:09am, the police incident was declared over and the northbound lanes reopened.
The southbound lanes have remained closed however.
Earlier one motorist that was a witness to the scene, but not directly involved in the incident, described the atmosphere as “very freaky” and confirmed that there were “loads of police, ambulances and emergency vehicles but no one is moving”.
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