A psychiatrist treating the singer contacted Los Angeles police to set the events in motion, celebrity website TMZ.com said, quoting law enforcement sources.
A Los Angeles Fire Department ambulance transporting the 26-year-old was escorted by dozens of police on motorcycles, accompanied by a police helicopter, the Los Angeles Times said.
The operation appeared to be thoroughly planned, it said.
A motorcade the length of a football field surrounded the pop star and kept photographers and onlookers at bay.
Spears was told of her impending confinement by her psychiatrist and did not resist when paramedics arrived and placed her on a gurney, TMZ said.
The doctor told police of concerns about her reckless driving and erratic behaviour.
Spears had not slept since Saturday, the website said.
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She was stripped of access to her two young boys at the beginning of January after another hospital drama.
During that incident Spears was wheeled out of her home on a stretcher after a stand-off that began when she reportedly refused to release her two children, Sean Preston, 2, and Jayden James, 1, to former husband Kevin Federline's bodyguard.
Spears was taken to the Cedars Sinai Medical Centre for mental evaluation before she discharged herself two days later.
The reasons for Spears' admission have not been revealed, although speculation has raged that the singer is suffering from a long-standing mental illness.
Spears, one of the most successful singers of her generation, has been locked in a custody fight with Federline since the couple separated in 2006.
A judge limited the star's access to her children in October after she failed to submit to random drug testing as demanded at an earlier hearing.
Her latest attempt to regain visiting rights to her two sons was rejected last week after she failed to appear for a Los Angeles court hearing.