The A1M is partially shut close to its York turn-off after a serious collision in the early hours.
Emergency services were called to the crash at 2.12am today (Wednesday).
Its was initially closed both ways between Junction 48 (Boroughbridge) and Junction 47 (Allerton Park).
It now remains shut southbound – but the northbound carriageway has reopened.
Traffic is being diverted via the A168 that runs parallel to the A1M.
North Yorkshire Police said: “We’re currently dealing with a serious RTC which occurred at approximately 02.12am this morning on the southbound carriageway of the A1.
“The southbound carriageway of the A1(M) is currently closed between junction 48 (Boroughbridge) and junction 47 (Allerton Park) and is expected to be for some time.
“The northbound carriageway was also closed for some time but it is now open again.”
At 9.32am, North Yorkshire Traffic Bureau tweeted: “Due to the A1(M) closure, there is a significant increase in traffic volumes on surrounding roads including A19, A168 and A64.
“Please give yourself extra time. If you need to re-programme satnavs or use your mobile phone, DO NOT do this whilst driving. Pull over and do this safely.”
We have no details of any casualties at this stage.