Police said they expected the southbound carriageway of the M40 to reopen at about 4pm today.
However, the northbound carriageway is likely to remain closed until at least 6pm.
Both lanes were closed following a collision between two lorries shortly after 3am in which one man died.
One of the lorries was carrying a shipment of lard, which has covered an area the size of a football pitch and is proving hard to remove from the road.
Police have urged drivers to avoid the M40, despite the carriageways’ reopening.
They have also asked motorists to avoid the A40, which has been used throughout the day as a diversion route, and the High Wycombe, Amersham and Beaconsfield areas.
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