Spears' tests free of illegal drugs

LOS ANGELES, Jan. 7 (UPI) -- Troubled U.S. pop star Britney Spears didn't test positive for illegal drugs or alcohol during her recent hospitalization, People.com reported Monday.

Spears spent two days at Cedars-Sinai Medical Center after police were called to her home because she refused to return her two young sons to their father at the end of a court-sanctioned, supervised visit Thursday evening.

Police said the singer appeared to be under the influence of "an unknown substance" at the time of the incident.

Spears was taken to the hospital for a psychological evaluation and drug tests.

"She tested clean," a source told People.com. "This lady is as clean as clean can be and has been for some time."

Two sources who know the Spears family told the magazine they believe the singer suffers from undiagnosed bipolar disorder.

One insider said Spears, 26, has "suffered from a psychological disease for years."

Spears left the hospital Saturday.