According to reports, when Kevin Federline’s bodyguard showed up to collect Sean Preston and Jayden James, Britney locked herself in the bathroom with both boys and wouldn’t come out. She also refused to let the boys leave, so cops were called to the house. A source told PageSix.com that Britney was "hysterical and just wanted to keep the kids overnight.”

And her drug tests came back negative for drugs and alcohol.

Life & Style can exclusively report that Britney Spears blood tests at Cedars-Sinai Medical Center came back negative, despite earlier reports from police that she appeared to be under the influence of a substance when she was taken from her home after a custody dispute last night.

“Her blood test just came back, and, thank God, it was clean. There are no traces of drugs or alcohol of any kind,” a source close to the Spears family tells Life & Style.

This indicates that her odd behavior was not the result of substance abuse, as early reports suggested.

Britney appeared to be laughing when she was taken from her home into an ambulance.

But an LAPD spokesperson was unable to confirm or deny to Life & Style on Friday morning that earlier reports indicated that cops believed Britney appeared to be under the influence of a substance when they arrived on the scene.

Britney Spears Meltdown