UPDATE (9:10 a.m.) - The lane closure was lifted a little around 9 a.m.
Northbound traffic on Hwy 101 is backed up between Nipomo and Arroyo Grande after CHP issued a SIG alert closing the second northbound lane.
The closure extends from Los Berros Rd. to Laetitia Winery, a CHP official told KSBY.
CHP says that they believe a subcontractor doing soil sampling in the area caused the slowdown during heavy morning traffic. Officials are working to clear the area before the road can reopen.
The closure was announced just after 7:30 a.m. Initial reports estimated the closure would lift by 9:30 a.m.
This is a developing story. Check back here for updates.