A driver suffered life-threatening injuries after multiple crashes caused a slowdown on Highway 20 in Nevada County Friday morning, authorities said. 

The California Highway Patrol said it responded to Highway 20 between Grass Valley and Penn Valley around 8 a.m. after a Volkswagen rear-ended a semi-truck. 

Just after that crash, CHP officers said a second crash happened when drivers tried to avoid the scene. 

The driver of the Volkswagen was extricated from the vehicle and taken to a local hospital via an air ambulance with life-threatening injuries, the CHP said. 

During the slowdown, two other minor crashes occurred, the CHP said. No serious injuries were reported in those crashes. 

Lane closures were in place for both directions for about an hour. 

The CHP is urging drivers to slow down, stay alert, avoid distractions and follow instructions from emergency personnel.