Highway 17 is closed in both directions in the Nairn area close, Fairbanks Road.
Police have yet to release any details, except to say the highway is closed in both directions while they carry out their investigation.
There are unconfirmed reports of a fatal collision.
The closure took place shortly after six pm Wednesday evening.
It is not known when the highway will reopen, but it is estimated it could be closed as long as six to eight hours.
Police are turning motorists around on the four-lane and are working on setting up detours (if possible).
