Britney Spears arrives at the Peninsula Hotel in Beverly Hills last night. She also she got a flat tire yesterday and the paps were there to rescue her (pics coming next post).

Meanwhile Britney has reportedly tested free of illegal drugs and alcohol.

The troubled star has been declared "clean" after allegedly undergoing blood and urine tests during her 72-hour stay at Los Angeles' Cedars-Sinai Medical Center.

A source revealed: "She tested clean. This lady is as clean as clean can be and has been for some time."

It has been claimed Britney went on a 36-hour binge of prescription and over-the-counter medication last week, during which she took 20 Clenbuterol diet pills, 18 herbal speed tablets, 18 Piriton anti-histamine tablets, 12 Vicodin painkillers, 10 sleeping pills and eight antacid reflux tablets.

The 'Gimme More' singer was taken to hospital following a three-hour stand-off with police which began at 8pm on Thursday after she refused to return her sons, two-year-old Sean Preston and one-year-old Jayden James, to ex-husband Kevin Federline.

When officers arrived at the residence they claimed Britney was "under the influence of an unknown substance".

The pop superstar was held under California's '5150 Hold' legislation - which allows people to be held for 72 hours for psychiatric evaluation if they are deemed "a danger to themselves or others".

She was released on Saturday following a psychological assessment.

A source close to the Spears family claims Britney has been suffering from a serious psychological illness for years, saying: "There is no question she has bipolar disorder. She's been having manic episodes for a long time."

Following the incident, Britney's ex-husband Kevin has been awarded sole custody of their sons.