UPDATE (4:40 p.m.) - The truck wreckage has been cleared from the highway.
UPDATE (12:34 p.m.) - The California Highway Patrol says no injuries were reported. Officers say speed may have been a contributing factor.
(11:37 a.m.) - A semi-truck crash on Highway 1 at Willow Road in the Nipomo/Arroyo Grande mesa area was reportedly blocking traffic Friday morning.
The crash happened at about 11:20 a.m.
The California Highway Patrol reported that the semi was on its side and blocking both lanes.
This is a developing story and will be updated with new information as it becomes available.