The A6089 road between Carfraemill and Gordon has been closed for more than five hours and is expected to remain closed for some time.
Police Scotland said no other vehicles were involved in the incident but has not confirmed if there are any casualties.
More than three fire engines, six police cars and at least five ambulances attended the scene.
A police spokesman said: “Officers are currently in attendance between Carfraemill and Gordon following a report that a minibus overturned at 10.50am.
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“Closures are in place in both directions and emergency services are on the scene.”