Immediate repairs have caused heavy delays on the A1(M)'s northbound carriageway near Stevenage and Welwyn Garden City.
The works - caused by a carriageway defect - began at around 5.15pm yesterday (Tuesday, March 19) between junctions 6 and 7.
Investigations have since been ongoing, with one lane closed on the motorway.
This morning (Wednesday, March 20) National Highways confirmed that delays had increased to 60 minutes.
National Highways have since confirmed that a full carriageway closure will take place tonight on the A1(M).
The northbound closure will take place between junctions 6 (The Clock) and 7 (Langley Sidings) from 9pm until 5am tomorrow morning (Thursday, March 21).
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A spokesperson for National Highways said: "National Highways has put the closure in place while assessments and repairs are carried out at the scene.
"The closure will allow further investigations work to source the issue.
While the closure is in place, drivers are strongly advised to allow more time for their journeys and to follow the diversion route signed."
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