UPDATE: Main Roads has advised the fog has cleared.
EARLIER: Roe Highway commuters have been urged to take caution after the road was hit by a heavy fog this morning.
The fog has reduced visibility in both directions between Tonkin Highway and Great Eastern Highway.
While the road is currently open and there is no known congestion, Main Roads have asked drivers to exercise extreme caution.
It is the second time in just over a week early morning fog has caused disruptions, with the Kwinana Freeway affected last Thursday.