A crash between a sport utility vehicle and another vehicle was reported on the highway around 2:40 p.m., CHP Officer Peter Van Eckhardt said.
The Nos. 1, 2 and 3 lanes of southbound 101 just south of Holly Street were blocked by the crash.
The SUV overturned in the collision, Van Eckhardt said.
One of the people involved in the crash called her mother to tell her about the crash, but the mother has been instructed to head to Stanford Hospital instead of the accident scene, Van Eckhardt said.
Two people from the SUV and one person from another vehicle were transported to the hospital. Two of the injured parties sustained minor injuries and one person was unconscious with major injuries.
A Sig-alert was issued around 2:50 p.m. and canceled around 3:45 p.m.