A lorry driver is understood to be trapped in his vehicle after it overturned.
The accident happened on the A9 Inverness to Thurso road at Berriedale Braes at about 11.30pm.
Police, fire and ambulance crews are currently at the scene, and are treating the incident as serious.
The road is currently closed – forcing vehicles transporting ballot boxes from Caithness to be rerouted via Melvich.
A police spokesman said: “Police Scotland is currently attending a serious road traffic collision on the A9 truck road at Berridale.
“The road is closed in both directions and is likely to remain so for some time.”
Bear Scotland is putting in a diversion, which will take northbound traffic onto the A897 at Helmsdale and southbound traffic via Thurso and the A836.
The diversion is not suitable for large vehicles however.
Once the vans make the trip, the refendum votes will be counted at Dingwall. It is not yet clear if the diversion will delay the results for the Highlands, which are due to be announced at 4am.
**This diversion is not suitable for large vehicles**
