North Yorkshire Police said the sinkhole began filling with water at the crossroads in Rillington at around 3.45pm on Sunday July 31.
The A64 was entirely closed after the road started "sinking" outside the Coach and Horses pub, they added.
National Highways said the A64 is closed eastbound between the A169 at Malton and the B1429 at Willerby and westbound between the B1429 and B1428 at Scagglethorpe due to a burst water main, which caused the road surface to collapse.
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Workmen from the authority and Yorkshire Water have been at the scene overnight to repair the damaged water main and large hole that has formed in the middle of the carriageway.
National Highways said the road is expected to be closed for at least 48 hours for emergency repairs to take place.
A National Highways spokesperson said: "the road is expected to be closed for a considerable amount of time".
Traffic is being diverted via local routes and drivers are urged to allow extra time for journeys and to plan ahead.