UPDATE (4:40 p.m.) - Sheriff's officials say the incident off Highway 41 on Friday afternoon turned out to be a spoof call.
The scene has been cleared and reopened to traffic.
(4:06 p.m.) - Highway 41 West is closed between Toro Creek Rd. and Old Morro Rd. because of law enforcement activity.
Authorities were called to the area of Highway 41 and Toro Creek Rd. shortly before 3:30 p.m. on Friday.
Multiple agencies were responding to the incident, including San Luis Obispo County Sheriff's Office, California Highway Patrol, and Atascadero Police Department.
Authorities would not immediately confirm any details about the nature of the call.
This is a developing story and will be updated with new information as it becomes available.