The North Carolina State Highway Patrol says a rock in a private driveway is to blame for a chain-reaction crash last week that injured two Durham police officers and a Durham County sheriff's deputy.

A wreck report released Monday said the crash began after Deputy Paul Aiken's 2013 Harley-Davidson motorcycle left South Lowell Road near rural Bahama on Tuesday.

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Aiken's motorcycle hit a rock, left the road and then hit a nearby utility pole.

Officer Larry Cox, who was also driving a 2013 Harley-Davidson, swerved to miss Aiken, ran off the road to the right, hit a ditch and overturned.

Officer Francisco Miguel DeVera-Rodriguez, who was operating a 2015 Harley-Davidson, traveled onto the northbound shoulder, struck a utility pole support wire and overturned.

According to Sheriff Michael Andrews, the officers and the deputy involved had recently concluded a funeral escort and were practicing their formations.

The three men were taken to Duke University Hospital for treatment. Aiken and Cox sustained minor injuries, and DeVera-Rodriguez suffered serious but non-life-threatening injuries, authorities said.

DeVera-Rodriguez remains hospitalized, while Aiken has already returned to duty. Cox is out of the hospital but not yet back on patrol.