The fire district wrote on Twitter at 7:46 a.m. about the incident taking place in the area of northbound Highway 101 near Atherton Avenue in Novato.
Novato Fire District is on scene for a HazMat incident NB 101 at Atherton. Unknown substance at this time. Updates to follow.— Novato Fire District (@NovatoFireDist) July 18, 2017
The Atherton/San Marin Overpass is closed due to hazmat incident.— Novato Fire District (@NovatoFireDist) July 18, 2017
The incident involved some sort of substance spilled on the roadway, according to the California Highway Patrol. No other details were immediately available.