LATEST: Britney Spears has been classed as a "special needs" patient following her admission to a Los Angeles hospital, after it emerged she locked one of her young sons in a room with her at her Los Angeles home. The troubled singer, 26, was admitted to the city's Cedars-Sinai Medical Center on Thursday evening (03Jan08) following a major stand-off with police at her Beverly Hills mansion after she refused to hand over her two boys to ex-husband Kevin Federline after a scheduled visit. Her court-appointed monitor called for emergency services after witnessing Spears' apparent mental breakdown. A source tells People.com, "She had already put Sean Preston in the car when Britney locked herself in a room with Jayden James. "The cops came and got through the door and tied her down to a gurney." And Spears is being kept under close watch at the hospital - she is being held on a "5150 hold" order, meaning medics have reason to believe she is a danger to herself or others. Various online gossip sites claim Spears has been identified as a "special needs" patient, a reference which is only used for those who have overdosed or attempted to commit suicide. Meanwhile, police are reported to have found Spears "under the influence of an unknown substance" after the incident - but further U.S. reports claim her drug test was negative. Life + Style magazine is reporting an insider as saying, "Her blood test just came back, and, thank God, it was clean. There are no traces of drugs or alcohol of any kind." Spears is expected to remain at the hospital for a minimum of 72-hours on lock down for mental evaluation, after going "completely psycho" when paramedics took her away in an ambulance. Another source tells Usmagazine.com, "They had to strap her down like a mental patient and she was going between laughing and hysterics. (It was) a total psychotic breakdown. She just went crazy."